I don't mean to throw a monkey wrench in this, but if you want a killer synth (actually 4 of them) and about 11 different drum tracks (kick,snare,hihat,etc..) then I would seriously... seriously look at getting the Radikal Spectralis. That thing is awesome and you get a LOT of kit. That's all you need. It is more expensive, but worth it.
RADIKAL TECHNOLOGIES - Spectralis Hybrid Synthesizer Spectralis :: Index
I had the Machinedrum for a while, but sold it. I was fun and a cool instrument, but I have the Quasimidi Polymorph, which the same guy Jorg Schaaf made the Spectralis, and it's the most fun and inspiring synth I own, well tied with my Sunsyn at least.
I think the Monomachine might have been a little more fun, just because I like to have a synth and drums teamed up with a sequencer - that way you can make whole songs if you wanted to or at least get a strong base (even though I like to mix different synths
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I've heard many say the Spectralis's synth are almost modular in design, they're so deep and you coax so much out of it. I should note that it has 1 analog synth and 3 polyphonic synths.
#1 to think about is what kind of box you want (a drum machine, 6 synths, or a combo of the 2) #2 do you like the 'sound' of one box over the others