Tube amps - what 3 things…

Ralph, stated another way, if the grid voltage remains constant as the transconductance changes, the current in a bipolar [CT] transformer will be unequal.

Seems like a greater evil... unless one is OTL 😉

The following might seem to be have a air of Negative as reply.

Note I have had a Tube Pre Amp > Power Amp in use since the 90's.

Tube Amp's command a slight alteration to the disciplines of use that can be used with a SS Amp'.

There is a concern for a occurrence where a fire could be the result.

A Drastic Statement it is, but anybody with a Long-Term experience around individuals with a Tube History, will pick up on the need to heed the above and express a 'Vigilance' when using a circuitry that has Tubes.

In a nutshell, when using Tubes it is best to know any early warnings something is amiss with a Tubes Function, it is most reassuring to be able to see the Tube as a operating component with the Power On.

'Vigilance' means being present and observant, aware of developments that suggests a Speedy Power Off Interception is for the best.

I have disciplined myself to be in full time attendance in the Listening Room , with only very short periods of absences during periods that the Tubes are Powered On.

If an individual like to have extended periods without a observation of the equipment in use, the use of Tubes might not be ideal for such practices.

All who I know with Tube Devices are very similar disciplined to myself, which has resulted in not personally knowing anybody who has had a fire in their set up system. I even know one individual who seen an Element start to glow more red than orange and did not suffer any serious outcome as a result of the immediate Power Off that was actioned. 

The same is not said for those I know that extend their use of Tubes to the place where they work with Tube Devices on the Workbench, I know of smoking circuits occurring. 

I do not ever see myself without a Tube Device in use, but recent years have certainly introduced myself to SS Amplification that in my assessment could be used in place of my Tube Equipment. I have already pretty much decided a retirement system to be created, may have a Second Power Amp and a few devices that are SS, as I don't have to be so attentive to these when in use.      

OP's  question is very good question, and it should go with any speakers. Don't limit the range of speakers when we reply the questions.

Here is my answer if you want to have a good setup.

1, tube power amplifier

2, tube crossover in the speakers.

3,tube preamp 

Choice 3 is optional, you might get SS preamp instead.

Here is the point with the speakers: some speakers has  separated crossover and could replace easily and if the crossover is inside the speakers, it is very different to replace.

The crossover has very strong point to the sound which can compare with preamplifier ,but in long time, we ignore it.look back the vintage UK speakers, they always have outside  crossover which let us to modify easily later.

I think there are great answers here.  OP don't be intimidated.  I have two tube amps now.  My main system is a PL Evo 400.  Nothing but good things to say about this AMP.  My second is a 'vintage' Grant Fidelity Rita - in my office and more of a hobby piece for me - would be just as happy SS there.

Piling on - I could live without the UL/Triode switching.  I stay on UL 99% of the time.  If i only had triode that would be fine too.

Auto-biasing a must for me.  I have many things to fill my time. 

I turn it on. Listen and love it.  Turn it off.  There is not stress, and limited tinkering if you don't want that.

About a year in I started getting a cracking noise out of one channel.  Pulled the tube and reseated it - problem solved (with AG community help).  A 20 minute exploration and deepened my understanding and learning...fun.

You can turn this into a full time rabbit hole hobby - but tubes do not need to rue your life.  

But I have a system that gives me chills, makes me laugh out loud, and is generally the most special "me time" thing in my life next to my cars.

Have fun with it.  with some modest research on amps and speakers there really are very few bad choices.

From what I hear DHT is right, but budget and such matter. Rule 1 though is GIGO, garbage in, garbage out. My system with an old PS Audio 200C or Acoustat 3l200 watt amp would sound good, but my Mark Levinson smokes them both. OTOH, if I had a $100 Schiit DAC in my system it would sound far worse than a TNT in it with the Lampizator DAC. The thing that I like though may not be what you like, so if I give you the correct answer it's dumb luck that we have similar taste in what we seek from music.