IMO the Fender 400PS is the best bargain for tube power, IF you do your homework. Rated at 435 watts RMS, I've read recently on the Yahoo mailing list that when set up to factory specs they put out closer to 600. You like your 8X10? A 400PS can power 3 of them. It can take some time to find the best cabs for it, since it takes 1-3 4 ohm loads - and only 4 ohm loads. These days, though, small 4 ohm cabs are pretty affordable from Avatar, Carvin, and the like. It took me a while to settle on my current cab combination - the Carvin Neo 2X10 and 2 Bag End D12E cabinets - but it's pretty lethal.
For solid state amps, old Acoustic stuff is crazy loud, especially if you match the head with their cabs. Sounds pretty great too. I used to think they were just boomy old amps, until I tried out a 320. Yowza!
For 200 watt or less tube amps, Sound City is sort of the poor man's Hiwatt. It won't stay clean for very long, but if you like fuzzy four string noises, they're pretty cool.