Building new system starting with power amp. What would you choose ?

This is not how it usually happens, but what if you simply must have a particular amp and then move with upgrades in both directions? Let's assume that the only source will be RTR deck, so no preamp will be needed.
The price about $15k new or used ?
This is a hypothetical exercise, I am personally not prepared for that yet. However, it would be, theoretically, perfect minimalist audiophile set-up. 
I myself would probably choose either Lamm monoblocks or Gryphon stereo power amp, both used of course.
A pair of the Levinson ML-2 (25 watt) monos. Plus a pair of Quad 57's. Designed by Tom Colangelo. Each mono amp weighs 100 lbs. No skimping here on the power supply!
If you 'must' have a particular amp, that most importantly affects your choice of speakers, i.e. amp's power will need ____ efficiency speaker, in your space, at your desired max volume. 

Even if what you 'must' have is powerful, I always recommend efficient speakers so you can eventually try tube amp(s) within an affordable power range where there is more options.


Pick your efficient speakers first! Within the 'efficient' category, find speakers you 'must' have. After speaker selection, knowing your space and volume preferences, you know how powerful an amp you will need. Then find an amp you 'must' have within that power category.

Enough power? IF not too much = less: money, heat, weight = more placement options.
The Levinson ML-2 mono amp has 1 Farad of capacitance in its cap bank! Something of a record here! And the ability to easily drive the 1 ohm Apogee Scintilla - a brutal load indeed! 200 watts @ 1 ohm!
Minimalist, but not totally:

I must have remote volume, mute, and remote balance from my listening refine individual tracks the engineer’s didn’t get perfect. Or the equipment/system isn't getting it perfectly. Balance, enjoy now, check everything in the morning.

A very small balance adjustment can make a large difference to imaging, not just the center i.e. singer, but more distinctive localization of backup singers, other musicians, giving a more involving experience.

Another advantage: If you learn to listen for, appreciate distinct instruments, imaging, then when it is OFF, it is not easy to ’let it go’.

R2R, you have individual volume settings L and R, watching meters is one thing, and who knows when matching signal strength l/r are correct using the beginning of a program’s content. delivered sound to your listening position is the real thing.
elliottbnewcombjr: the OP wants an amplifier as a starting point for building a system around. Strictly a fantasy exercise! So I offered a great classic amp from the past and two radically different speakers that can work with it!
This is not a theoretical exercise for me.  I'm there.  I didn't exactly start with my amps, which are Atma-Sphere M-60s, but anything I do going forward will start with these amps.  I might as well pour concrete around them.  They aren't going anywhere. 
A ZOTL amplifier of David Berning....

No question, what else?

It is the only tube amplifier, with almost illimited tube life, no heat, and the qualities of tube amplifier+ S.S. design.... Price at low level /high quality

Pairing them with a pair of speakers i dont know which to chose yet...
Good luck with that i will always have great preamp(Audia Flight Stremento #1 mk2) and tube phono stage(TW ACUSTIC RPS 100).
Gryphon is what immediately came to mind as soon as I read your notional budget. The Diablo is hard to beat for overall sound quality in a neat package, especially if you have no desire to fuss with tubes. Solid state really doesn’t get any better at that price point.

I personally might do an Ayre or a D'Agostino.  however, I'd definitely have speakers in mind.

What I normally suggest people listen to are:

  • Ayre
  • Luxman
  • Pass
  • D'Agostino

This gives a nice spread of amps and sound qualities.  Luxman and D'Agostino more similar than not, Pass and Ayre taking decidedly different approaches.

If I was going to use a high efficiency Klipsch, Tannoy or Altec type of set up Pass would be high on my list, but honestly I tend to stick to small footprint conventional multi-way speakers. Wilson's being among the largest I'd consider.
Levinson ML-2 is a great idea. Can it still be serviced ? I read about it but never heard it.
Gryphon Diablo is yes, basically a power amp with passive preamp. However, I would try to find used Gryphon Class A power amp. instead of it first.
Sanders sound Magtech mono blocs. 
 Any warm speaker. (86-90 db 1w/1m)
 CJ  ET5 SE. 
 Rotel 1572 CD player.Audioquest cables.

 8 ga speaker cables.

 Bottle of Bushmills 21yr single malt Irish whisky!
Can of Copenhagen long cut.

 Leave me alone!!!!
Oh, I missed the point, what would WE choose? What would I choose?. 

I thought you meant, you had already see an amp you 'must' have.

15k budget, that's more than I would spend, I have efficient speakers, so I have the advantage of staying in 25, 35-45 wpc range which are more affordable.

I researched, chose my Cayin, love it, it never occurs to me to consider another. That left me with 12K to spend on other stuff. Well, I would like external bias adjusters and meters.
Based upon childhood memories (Leak)...

A properly refurbished Leak ST 20 (might need a quality repop PT in the redo) paired with contemporary easy to drive speakers.

Also intrigued by the less expensive David Berning/LTA offerings but have only briefly listened to a couple of his amps (the last being maybe 15 years ago and the other way before that).

I recently posted about a Roger Modjeski EL84 based power amp that I also find special in that it's sound was different, but also incredibly pleasing instead of odd.

It didn't seem to to compress with busy source material and instead remained 3D/open (and this from 2 EL84's per channel).

Not up on new stuff (as you can imagine by my posted rig).

Go to your favorite audio dealer(s) and listen.  Learn.  Observe.  Make a judgement.

Just keep in mind that tube amps require care and feeding that solid state amps do not.  Depending of the rest of your system, a very good solid state amp will give you as much satisfaction as a tube amp without the tube amp hassle.
I have a Krell KSA-80B which sounds even better than an ML-2.  It puts 640 watts into my One Ohm Apogee Scintillas.  It never strains.  Its very musical.  I had it factory recapped a couple of years ago.  Its my amp for life.
I'd like the Sim audio amps myself very neutral warm sounding. The w8 was phenomenal.
i love my Magtech. Fyi, your suggestion is the reason i looked into sanders. Im not sure how any other amp could be better. Nothing ive heard at least.
It don't work that way. You have to decide what speakers you can live with. Then get an amp that feeds them what they want. And why oh why do you think that you don't want a preamp?
When tape deck with volume control is your source you don’t need a preamp. Electrically must be matched, though.
misguided concept from the start

why not build a system around cables you love?  🤔
Anyway, I do have speakers in my mind that I would consider first, if I could find them used - Kharma.
My fantasy amp brand is NAGRA. If I win the lottery, I want to have all-Nagra electronics. 
Both your initial choices are great, although I would look for the Lamm first before moving to Gryphon.
 Personally I would never start with an amp. If already knowing the budget and room: I'd start with speakers.
 That aside, and playing along, if I were to start with an amp already knowing the lone source and without a preamp, i.e. RTR deck,: I would seek out an an amp with an input impedance, and sensitivity for maximum output that would suitably match the output impedance and voltage output of said lone source (RTR deck) with as much power as I might need. 
A pair of Classe DR3 VHC amplifiers used in monoblock configuration gives 100 watts
of Class A power per channel.  These were designed to drive the notoriously inefficient
Apogee Scintilla at its 1 ohm setting.  A used pair of DR3 VHC's should cost you
about $4000.  New in 1987 they were about $4300 each.  
Solid State: Ampzilla Monoblocks or PassLabs amps.  I have both.  Have the 250.5 PL amp- great sounding, presents solid state in a most pleasurable way.  Only problem is it weighs 100 pounds.  Just picked up a 150.5 PL amp.

Tube: Canary Monoblocks.  I have a pair of 140 wpc that were good stock and are outstanding after modification by Asi Teknology.  Decware Anniversary Mystery Amp.  If you have moderately sensitive speakers this 40 wpc amp sounds fantastic. I drove to Peoria, IL to listen to them.  

My experience is limited to what I have owned or heard elsewhere.  I know there are many other fine amps out there.
You must chose the room first, not the amplifier, not the speakers....

No educated listenings ears give a dam about the gear, give me anything, or almost, and i will make it sound good...

It is called embeddings controls and treatment of the working dimensions of the audio system...

Any fixation on a piece of gear is an obsession, call it a taste if you want, but acoustic, mechanic and electricity are the 3 playing ground....

Read me right, i love my Sansui Au 7700, but the room/ears/brain is the main component....
The room we have, is the room we have for most people.  It can be treated in many was, but realistically, unless you are moving, most people are locked into their room.

If you choose your power amp first, you clearly are limiting your speaker choices, and vice versa.  I own Maggies, thus eliminating many amplifier choices and I am good with that.  My amps are McIntosh MC501s and the combination has pleased me for the last 15 years.

Good luck with your selections as building a system is a great joy.
The room we have, is the room we have for most people.
You are right...

I am lucky because i could acoustically transformed my room for my audio system... At no cost at all.... Esthetic dont matter in my audio room ....

But if your audio room is the living room, it is nearly impossible to install at low cost treatament and controls of the room that are cheap.... Esthetic means often costly... i imagine that it is possible anyway in a living room in some case of positive geometry, positive topology, and positive acoustical content materials...

stibi, I agree with you, I would consider Lamm first. Question is which one.
Diablo 300 is a very fine choice if you want transistor amp, and it can easily be found used, there are couple here right now. 

What if someone special gave you your favorite amp as a gift ? You would want to start building the new system from this, right ?
Another thought. Many speakers are actually better than they might seem but they do not perform their best because the amplification is not good enough.
Lamm, Gryphon, Nagra, D'Agostino would work very well with a wide range of speakers. Not sure about Levinson ML-2, besides try to find it, I guess.
The room you have; might not be suitable for the speakers you're considering.  The room might very well be the reason to reconsider a specific speaker for one that will work within it.
That might be another reason to start with the amp. Room might change, speakers might have to be replaced, but your favorite amp will stay.
In my case, I will never have very big room and I listen at moderate levels.
Purifi by VTV at <$1500 or spend a little more and get the NAD  version, giant killers
The only amp I “simply must have” is the one that works best with the speakers I love.  My audio DNA just don’t work the other way ‘round.  A couple that might get me thinking a little though would be the Valvet A4e mono blocks or maybe a Raven tube amp.   
If my room changed and it required changing speakers, I’d probably change amps to match my new speakers.

the Magtech is amazing!
will drive any speaker you hook up!
  One of the best kept,secrets in audio. 
 Enjoy one of the best amplifiers made!
im glad I could help.

 Enjoy the Magtech! A lifetime of perfection!

IMHO speakers have the most influence in the overall sound and character of a system. If you’re already set on your source (RTR) then speakers logically would be the next step. Pick your "sound" and THEN get the requisite electronics. Bookshelf or floor standers? Traditional box speakers or planar? All of those will likely require different electronics to sound their best. With regards to no preamp, I’d reconsider that. For one thing you’ve completely forgone any flexibility with regards to any other sources, not to mention any convenience features like a remote. (Unless your R2R has one) In any case, enjoy the hunt!
Happy listening...
I have several vintage class A amps but I’m always looking for others. I have been looking for Levinson ML-2s. Not easy to find. I’m betting they are very expensive to update. Good luck finding a pair of the Classe DR3s. I’ve seen one for sale in 6 months. If those above are on your list then look for Krell KSA units too. 
I have always built my systems around the PS Audio power port or Cryoed Hubble outlet.😁
Pass Labs INT250. Nothing else will even come close. Add a phono preamp and a DAC and you are set.
Crazy that No one mentions the excellent Sugden A21se. They started it all when it comes to SS class A well over 50 years ago. At $3250, a bargain in my eyes. Pair it with some nice Tannoys and a tubed phono stage and I'm certain you will be very well pleased.