I use an EMX512, and IMO it's a bloody brilliant bit of kit !
2 x 500W power amps, can be used one per side or, as I use it, one to drive the FOH and one for monitors. It only does a single monitor mix, but we only usually put vocals through the PA anyway, sometimes a bit of kick.
The onboard effects are very usable (eg bit of reverb on the vox) and the single knob compressors sound surprisingly good if you don't go silly with 'em.
A big plus for me, as sorting this stuff seems to be the bassist job by law, its simplicity. One box, mic's in the front, speaker leads in the back. Job done.
And it sounds good too.
Used ones seem to go for 200-250 wuid.