How to pick a tubed integrated without hearing one

For $1k used there are not a lot of choices, unless you look at some of the Chinese brands, which tend to have pretty poor resale value.

The only 2 brands I'd consider at your budget is the Rogue Audio Cronus Magnum, or the Primaluna Prologue one or two.

Both are well built, reliable and sound good.

As far as tubes go, it really depends on the power you need - 300b and EL34's sound the best, but are low powered - usually under 30wpc. KT88's are also popular at that price point - they are less tubey sounding, but offer more power.

As long as you use a moderately efficient speaker with an 8 ohm nominal impedance, you should be fine with 20-25wpc in a room your size (unless you like to rattle the walls). Subjectively, a 20wpc tube amp will have about the same power as a 50-60wpc solid state amp.

I have three comments:
1- You can look at all of the brochures and online specs, but there is no substitute to listening to an actual amp; preferably in your room with your speakers. I know that this is difficult in your case, but to do otherwise is just rolling the dice. TANSTAAFL

2- How many sources will you be using? If just one (CD player, media server, phono stage, etc.) you can save some money by considering a tube amp w/ gain (or volume) control. One inexpensive example is the Sophia Baby amp, which should run you under $500 used. If you can stretch your budget a bit, the Conrad Johnson CAV-50 is one of the best built and nicest sounding integrated amps ever made. And it will hold it's resale value better than most. But there are lots of other great choices if you consider new, used and vintage.

3- Speakers are key; some (like me) would say that the speaker choice is more critical then the amp. Most (but not all) modern bookshelf speakers are of medium efficiency and do not sound best with low powered tube amps. Do you already have speakers that you are planning to use?

Take any of them, of those that Meiwan mentioned. I would get Rogue.

Develop a short list of potential amps, and then read everything you can about each of them. Look at the "professional" reviews as well as user comments on the various audio forums.

Hopefully you'll develop a sense of what attributes are important and have a better feeling about your purchase.

I use the Sophia Electric Baby that Br3098 mentioned. I run 92db towers in a room 17x30. Not a rock concert levels but loud enough that the conversation volume increases sometimes. Don't worry about the single set of inputs, I use a Kramer vs55se switcher for tuner, cd and phono preamp.