Tube amps - what 3 things…

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.

A lot of good advice from the group here, although it doesn't necessarily square 100% with my experience, especially those who commented on impedance issues, tube life, and noise.  I have two primary systems designed around the use of high and low-medium efficiency speakers, Altec 604 and Magnepan 3.6.  I use tube amps from 1.5 wpc to 35 wpc with the Altecs, and tube and SS amps with the Maggies, tube preamp in both cases, and power output from the mid 50s to 120 wpc.  The two SS amps I have range from 150 - 200 wpc.  They all sound great because they're the keepers of the dozens of amps I've vetted. 

The key is choose your speakers first.  Then let the speakers drive the amp options.  My tube amps don't care if they're running 4 ohm or 8 ohm loads, have had both, and the 4 ohm loads do not cause any issues with greater loading, heating, etc, with the tube amps, but yes, the SS amps run hotter with the 4 ohm load.  As far as tube life, I run primarily old stock and NOS tubes and since I only listen seriously a couple hours a day, they seem to last forever.  I can't recall the last time one of my tube amps was noisy for any reason.  With the Maggies' lower sensitivity,  tube amps are dead quiet.  With the Altecs, there's a tiny bit of hum with the SET amp, and the rest are nearly silent.

Also great advice from those who said to avoid amps with proprietary or single source, or otherwise rare tubes.  If an audition with your speaker choice is possible, then you'll be sure you're getting the best matchup for your audio investment.  Have fun shopping!

For me autobias isn’t critical as long as it’s easily adjusted. I’ve owned Unison, Allnic, Quicksilver and Audio Research. My favorite sounding was my AR which is a pain to bias but the others provided an accessible dial. Biasing once tubes are settled should be monthly. Stick with a company that has been on the market for a while and has a solid support network. Buy an extra set of tubes or two and you should be set for a decade provided the amp isn’t left on. Good tube amp hygiene, no turning on and off in quick succession and allow a 15 minute warm up or more before hammering the system.