liverevolution, Yamaha's DTX has 3 series and each are of different levels (and budget) xD
DTXplorer is the entry level, good if you're starting out.
DTXxpress.. Erm, I'm not too sure, but its a mid-end set.
DTXtreme..Heh, 5k for the whole set and you get to play all sorts of funky stuff. Akira Jimbo does his one-band man feat with 2 modules of DTXtreme, elec pads and triggers on his acoustic. Crazy stuff :x
anyways, to TS: if you looking for elec drumkit, 600 is quite pretty low for really good ones. average selling price I've seen was 800 for the DTXplorer.