There's a TON of great small tube combos on the market, don't necessarily limit to something that has one of your favorite players' signatures on it.
I'm a big fan of tube amps in the 30-50 watt range. If you're not used to tubes, trust me, you almost definitely won't need more than 30 watts, tubes are SIGNIFICANTLY louder than solid state amps. I'm a little fuzzy on the actual physics, but as I understand it, solid state amps are designed to max out their power amp sections while staying as close to 0% THD (total harmonic distortion) as possible. Tube amps, on the other hand, are designed from the ground up with power amp distortion in mind - that's the whole point of a tube amp. So, at the point where a tube amp is just beginning to clip (say, 3 on the volume knob), you're typical solid state amp is already at 10.
Amps I generally recommend in this class:
Fender Hot Rod 30
Fender blues Junior
Peavey Classic 30
Mesa Lone Star Special
there's also some good Laney stuff out there, but I'm not familiar enough to recommend anything by model.
Some of it's pricey (the Lone Star Special may be the worst, at probably around $1200), some's fairly affordable. On the UBER-affordable side, Crate's VC tube stuff is actually fairly decent for the price, and if you don't need a "modern" crunch sound, the Fender Blues Jr. amp has a SWEET liquid overdrive, could totally cop a "Warm Regards" sort of Vai tone.
On the other hand, if you don't need tubes, and want a small, portable amp, check out Tech-21's Trademark-10. This thing never ceases to amaze me - ten solid state watts and an 8" speaker make it too small for gigging or jamming with a drummer (unless you're going to mic up), but I've been itching to grab one as a practice/recording amp, as it's the best sounding small solid state combo I've run across, hands down. the Trademark-60 is a bit pricier ansd definitely more vintage-voiced, but has enough power to gig (and it and a strat got me closer to SRV territory at conversational volumes than even a few older cranked up fenders I've tried).
By the way, you mentioned liking my tones in that XT thread - ALC was cut mostly with a Mesa Rocket-44 (discontinued, but pretty cheap if you can find them, and a great amp - lvery reminiscent of a stripped-down Mark-IV. I sold mine to Matt's Music like 2 years ago, if you're REALLY lucky he might still have it) and APP was done with a Nomad-45. Food for thought...
Yikes, long post. Late night at work, can you tell?