I just picked up an Obey70 on CL for $60. Rackmount, MIDI, DMX. 40 will do that too, I believe, and they make one with built-in DFi
I saw the Obey 40 w/ D'Fi. I'd prefer a standard 1U device rather than the top mount style of the Obey series. The 40 is 3.5" tall so it would be 2U if I stuck it on a shelf, but possibly 3U depending on how close the controls are to the device above. I'm definitely going to keep it on the short list though.
Ideally I'd like to mount in it my amp rack which is 4U worth of stuff, so at a minimum I'd be looking at a 6U or 8U rack.
I'd be good with a PC based controller as long is it had MIDI and the ability to run as a standalone device. I.E. program it at home, then bring it to a gig without a computer.