If you have a modeler (like tonelab, boss, Axe FX, etc) you can get a rack with just a power-amp. A good solution is the Marshall EL84 20/20, which is just 1U and very affordable. People say that the deep switch compensates for lack of bottom end.
In the mid range there are the Carvin T100, and used ones like Mesa 50:50 (supposed to sound better than 2:50), sometimes a Randall pops up (they run EL34 in one side, 6L6 on the other and you can switch them via MIDI, pretty cool).
For bargain and value you should look for one of the Reussenzehn amps, they are big and heavy but sound great and go for 300-400 (German built). Reussenzehn has also a new product which is an dual class A EL34 poweramp, supposed to be amazing (according to German Gitarre und Bass magazine), really light too:
http://www.reussenzehn.de/roehrenverstaerker/Vorverstaerker/DE/content?cont_id=299&Grp_id=6For above 600 you should look at the VHTs (I have a 2502). 2502 if you like EL34s, 2902 if you want bone crushing 5881 power. Currently guitarguitar are dumping out a 2902 for 799, which is 30% below usual retail.
There are several more options, like the Marshall EL34 50/50 or 100/100, but they are so heavy and big, you could also get a head instead.