Which new amp to get?

I’m thinking of getting a new power amp to replace my 25 year old Audio Research VT 130 SE.  My other equipment includes KEF Reference 5 speakers, Audio Research LS 22 preamp, Audio Research PH 3 phono stage,  Innuous Zenith 3 server, and Auralic DAC. My room is about 24 x 18.  I’d like to keep using the Audio Research preamp and phono stage, and I’m leaning towards a solid state amp more because of convenience than for sound. I’ve received several good recommendations from dealers but am getting confused by all the choices.  So far, here are the nominees: Coda 8, Krell duo 175xd, McIntosh mc312, ps audio bhk250.  All are solid state in the $6-7,000 range, which is my price point .   Other suggestions have been Airtight (tubes and expensive) and Audio Research (more tubes and they make the VT80 for $9500.. possibly not enough power..but the next step up is close to $20,000).  I’m open to considering others.  Mainly, I want an amp that’s long lasting and low maintenance, pairs well with my preamp and phono stage, and compliments the KEF speakers, especially their great imaging and sound stage.  I’d appreciate any input and also hearing from those who own some of these components.  Thanks. 
Years ago I went from a VT200 to SS amps. Krell, Pass, and Musical Fidelity, all great in their own way. I still have the Pass and MF amps. Eventually I went back to ARC with a Ref 110. For me the occasional biasing and tube replacement is worth it.

With the solid state amps I always felt like something was missing. It’s hard to explain but the Ref 110 gets me closer than the SS amps ever did.

No doubt the convenience of SS is great. Not counting the hours on the tubes or rushing to turn the amp off to save hours is great. Not to mention less heat. Right now, for me, I’m loving my ARC amp.

Maybe  try auditioning a newer used Audio Research amp while you’re at it. You might change your mind about the convenience factor.
Long-lasting and low maintenance sounds like SS to me. About 18 months ago, I listened to a few solid-state amps roughly in your price category. I was then using a Classe CP-800 preamp to Janszen electrostatic speakers. Here are my three favorites--

I liked the Pass X250.8 very much, with its creamy midrange. I had to send it back because of the heat. Your room may tolerate that better than mine, and if so, I suggest you give it a listen. Reno Hifi is a good dealer IMO.

A second favorite for sound was the Classe CA-2300, now discontinued (or about to be). I sent *that* back because I could hear the fan running in quiet passages of string quartets. Other than that, I found it a highly musical amp, unflappable and really enjoyable.

So much for amps with excess emissions!

I finally decided on a Bryston 4B3 -- you might prefer the next larger model. They are very reliable, and with the "3" (also called cubed) series, Bryston has got a very refined sound. Unless you just don’t want a Bryston, I suggest an audition. You might like it as much as I do!

You’ve got a fun problem to solve. Have fun solving it!

I'm a real fan of Luxman. Any ARC you buy now will sound pretty different than what you have. Considered an ARC integrated??
For the money, the Musical Fidelity M8s are pretty awesome.  The M8 500 is a great stereo amp and the M8 700s are really nice mono-blocks. 

$5000 for the M8-500 and $9000 for a pair of the M8-700s.  Smooth and detailed while being decidedly neutral.  

My next choice would be the PS Audio.  I looked at it seriously before moving completely to tube gear.  You will almost immediately want to get new tubes for the BHK as the stock tubes leave something to be desired but it is a great amp.  
Why not ask ARC for a price on a rebuild? You VT-130SE is a damn fine amp. I'd swap out the LS-22 for a Ref 5SE or Ref 6.
The nice thing about a lot of modern high end tube amps is the Fault Protection and Auto Biasing features.  The OP has invested at lot in ARC maybe keep it all in the family.
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I sold my $11,000 pair of Classe monoblocks and got the ps audio bhk250. Great amp. Try it with the default tubes and then get an updated pair so you can use the default tubes as backup. The bhk 250 has a lot going for it: quality parts, 4 speaker posts for bi-wiring, great SQ, and quite a bit of power.
Zesto Audio Bia amp is a great, easy to use (no fuss) tube amp.  Though I know solid state is what you seem to be targeting
They didn’t get much press when they came out but maybe look at the Audio Research DS225 or DS450. I have the DS225 paired with a Dac8, LS25Mk2 and a pair of ProAc Response 2.5 and they really shine with that ARC magic.

How about a custom built tube hybrid power amp? All point-to-point wiring, Class A output, V-Caps & Nichicon capacitors, Amtrans and Caddock resistors, AC filter choke, (2) 6SN7 tubes, 1 per channel and (2) 80 type regulator tubes, 1 per channel, bi-polar output transistors? See my system listed here and look for Vu Jade Custom Tube Hybrid Power amplifier.  I can offer you a trial period also.

Happy Listening.

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If you are dead set on SS try the Anthem P2 no fan runs at room temperature and built solid to last many years, or if you want to stay with tubes the Raven Shadow MK2 is a really great sounding amp.
Krell Duo 175 XD. With your existing preamp, it should be the full bodied, musical at that price point, hands down. The new XD line is looking quite good.
If you can buy a used item..... D’agostino Classic 2 stereo amplifier I found for $8,500
300 watts/ch
108 lbs. Great reviews
Get a female dog, a make horse and a tube preamp
paired with a solid state amp.

BidD's suggestion is a good one in my book! Scoring a DD at $8500
when the progression goes for $22k new is a wise move.

The Anthem gear has a room correction feature which
might offset the absence of tubes. 

Get at least 250 WPC so clipping will be infrequent.

Love to hear it once it is done!!
The new Hegel 390 maybe a good choice in your $6K range. Though in the review of the Hegel 590 ($11K) the reviewer said it was not dead silent like the Gryphon Diablo 300. I assume the 390 is also not dead silent.

I only mention the Hegel because Hegel is making a big marketing deal about KEF + Hegel together forever in happy bliss.
A Class-A amp that may sound truly special with your speakers is the Valvet A4 Mkll.  They are monoblocks that are rated at 55Wpc and 90Wpc into 8 and 4 Ohms, respectively, but with large power supplies they punch well above their weight.  And according to Stereophile measurements your Ref 5s are relatively amp friendly given forgiving phase angles 89dB sensitivity.  At $7850 new the Valvets are not much above the upper end of your price range. 

Another amp that flies under the radar but would likely make your KEFs sing is the Clayton Audio S100 that delivers 100Wpc of pure Class A power and has a convenient low bias switch so power consumption and heat are reduced when not using the amp for critical listening.  At $8500 MSRP it's a bit above your price range (isn't that always the way?) but is a serious amp and at least worth a look.  Personally I'd take Clayton over a Pass amp, but that's me.

Hope this is at least somewhat useful, and best of luck in your search. 
I have a EVS 1200 on order, should ship soon. Dual mono 600wpc newest IceEdge class D a mere $2200, though I expect that to jump soon

oh 30 day money back including return shipping 

How can you lose?
Strapped Benchmark AHB2s was a good suggestion. Of the three you mentioned I would go with the Krell. 

Good question.  My Audio Research amp sounds good.  I’m thinking of replacing it because it’s 25 years old and because of issues inherent to tubes...heat, warm up time, concerns about leaving it on, and periodic tube replacement. Sometimes I think it would be nice to have an amp that doesn’t require any care and feeding.  

I really appreciate all the advice posted here and all the people who wished me good luck. I have to say that I was confused before by all the choices and the great suggestions here do add to
the confusion.  I’m inclined to put Coda, Krell, Bryston and PS Audio on the short list.  I’m a little reluctant to go with some of the very small,lesser known brands which have been mentioned.  Any Coda 8 owners out there?  For Krell owners,any issues with fan noise?  Thanks again to all who have helped!  You guys are great.  

@fast Just remember the Kef’s are really at the best when with an amp with power. Even the little LS50’s need some juice to make them sing. 
 I had the Ref 3’s which was a love/hate affair until I finally got rid of them but prior I went thru many amps to try and get them to work. Just some were AR, Sim, Octave, Parasound, Modright and Bat. Finally wound up with MC452 which I really liked an almost considered keeping the Kefs but sold them for what I bought them as demo’s for. There are great deals on the MC452 since the MC462 came out which is well within your budget.  
trknomo, Mcintosh is a controversial brand, many people do not like their sound at all. The entire concept of an autotransformer is completely out of place with a solid state amplfier. 

If you are not aware an autotransformer is a load matching device used in tube amplifiers to impedance match the output from the high output impedance tube to the low impedance loudspeaker. 

A well designed solid state amplifier doesn't need a load matching device, if you build your output stage well you can power an arc welder with a solids state amplifier. 

Most solid state manufacturers do not use this concept as your speakers are now seeing an additional unknown feet of wire wound in that transformer for this reason Mac solid state amplifier have a warm punchy sound, however that trade off is you lose transparency.

The new Krell amplifiers are both warm and full bodied yet have great transparency for an amplifier in this price range. The Krell amplifiers are run Class A which generates that smooth lush sound yet with Ibias the amplifier run a bit cooler then traditional high power Class A amplifiers.

Benchmarks amplifers just sound tipped up and lack the subtitily that a really great amplifier does, they are great cheapie amplifiers if you have a warm speaker the Benchmarks are great, for a cleaner more neutral speaker like the Kefs a warmer more full bodied solid state amplifier would be our choice that is a Coda or a Krell, not a Bryston or a Benchmark. 

As per your setup it is all about system matching without knowing your preamp, digital, cables or other information it is hard to speculate to why you prefered the Mc over the other amplifiers. 

In our tests with the Kef Reference 5 the Krell was the best sounding amplifier for the price range. 

Dave and Troy
Audio Doctor NJ Kef and Krell dealers
From a tube/vinyl proponent, the closest I have come to the organic realism of tubes in a solid-state amp was delivered by the cult classic three in my book- Forte 4 with Soderberg mods, Bedini and BEL.  To attempt to understand my bias I think the top of the tube heap is the Coincident SET and Coincident Dragons- that is what I compared lots of SS amps to (including audio research, Carver, Sunfire, Moscode, Counterpoint, etc.). Instead of dropping serious coin on new amps, try a used one of those- all can be had for around $1000. Compared directly in a digital system - not mine- against Pass Labs X250 monoblocks, each of these amps performed quite well, garnering split decisions among my buddies
I just ordered the Coda .8 ..  Supposed to ship Monday.. Version 1 - 150 watt.. I've owned Parasound A21, Classe CA2200, older Krell, so I can only compare to them..  My other stuff currently is Parasound JC2-BP for preamp, Modwright Oppo205 (with NOS Mullard tubes) with everything feeding into that, and speakers Salk Sound - Song3a and some good cabling so I don't think anything will be holding back the sound from showing through.. I can offer my 2 cents in about a week.. I can't wait.. 
Congratulations.  Hope you will post a review when you’ve had enough time to evaluate it.  Meanwhile, have fun.