I've got a Boss Dr. Synth so yeah, good choice.
Not sure about the features of the others and whether they still carry the same models but mine has about 7 drum kits and full GM MIDI + built in chorus & reverb. I used it for about 5 years before uprgrading to software based stuff. I still use it now if I want to work on keyboard parts without worrying about latency delays. Check eBay.