carvin legacy or peavey jsx.
You and everyone else on this board.
A decent tube amp is definitely worth the investment, IMO. one thought on wattage - odds are, you'll want something pretty low. 30 watts is about ideal for a good combo, IMO. This is the first mistake everyone makes when they buy their first "good" tube amp, thinking that you need 100 watts simply because you needed close to that for gigging volume with solid state. Tube amps are LOUD. I'm currently playing a Mesa Nomad-45 2x12, and honestly I wish it had a half-power switch. I rarely turn it up past 2-3, and when gigging with it have never had to bring the volume up even as high as halfway. Lower wattage compresses more and gives you a rounder, spongier response - imo, a VERY good thing, and the entire point of going tube in the first place.
100 or more watts is complete overkill for anything smaller than a stadium.
Good small tube combos -
Mesa Lone Star Special
Marshall DSL 401
Peavey Classic 30
Fender Hot Rod Deluxe 30
Fender Blues Jr.
Laney makes some pretty good stuff too, but I'm not familiar enough to recommend anything by name.
Also keep your eyes out for more exotic stuff - Bogner makes a few small combos, and I gave a Soldano 1x12 a try once that was quite good, especially for the money (no idea what model, but they were looking about $800, and it was covered in purple tolex, if anyone is good with soldanos... Not surprisingly, great marshally leads.
Tubes aren't the ONLY way to go, of course - generally I've been pretty underwhelmed by most modelers, but I've always been impressed by Tech-21's stuff. Course, I also don't think it's fair to call them "modelling" amps, and honestly this is part of the reason why I've been impressed by them, I'd imagine.