You can pick up a used Peavy Classic 50/50 for around $300. *I have tried out some gear through one at a
music store and I liked it, especially for the price. *They also have mono versions at 50 watts and 100 watts. *If you don't need stereo, these would be really good buys. *I also have seen Mesa 50/50 power amps go for around $300 so keep your eyes open. *I would personally stay away from Marshall's or Mesa's 20/20 power amps. *They are Class A amps and just aren't my thing, but they might be yours, try them if you can find them. *Carvin used to make a tube power amp. *Could probably find one cheap if you can find one.
Although they are solid state, some other good power amps are the Mosvalve as mentioned. (I have one and it's really good, especially for the money, I only paid $125 used.) *ADA microtube amps (with a tube driver stage.) *Rocktron Velocity amps *(get one with a resonance control, whew, I got goosebumps with that one.) *
Stick with tube if you possibly can. *I would rather have a Solid State preamp driving a Tube power amp instead of the other way around. *Listen to the compression Satch gets when he digs in and you'll see why. *(sweet stuff)
Cool,
KO