I thought Roland had the lock on that racket. Do you have a used instrument store nearby? While its not that near to me, Atomic Music in College Park MD is amazing, and the prices are much cheaper than the same stuff new.
Meh, I've never seen electronic drums at the used places.
Roland does have a pretty big share on the midi drum market. I'd consider buying of theirs, but I've read some negative remarks about makers other than Yamaha or Roland.
The key, if you are more than just banging around, is to be able to use the pads to trigger more serious sound sample libraries, the FM synth sounds get old fast. DFH (drumkit from hell) gets good reviews from the drummers.