For composition, it's not really a big issue. There, you have time to shoehorn the different elements together, preferably with a computer DAW at the center, to help everything talk to each other and integrate it all.

But if you are talking about doing it all AT THE SAME TIME, it can get tricky. I like leeboy's idea of using the WS to be the controller (so don't get a rack!), that could be quite doable. I have always wanted to turn my G70/K2500 into a big �ber-arranger, but the weight of the K2500 makes my G70 feel like a featherweight! Too much to lug to a gig!

But you are going to have to be a bit of a MIDI guru to get them to talk to each other in exactly the way that each wants. If you have a decent working knowledge of CC codes, controller assignments and maybe a bit of sys-ex, it ought to be relatively easy. If you are bit more of a tyro it might be a bit more of a struggle.

Using each, one at a time is no hassle. But if you want to have the arranger engine running, AND the groove loops and KARMA all churning away at the same time under live control, be prepared to spend some time setting all that up.

The Kronos looks VERY promising, and Korg don't usually stint on the MIDI flexibility, so if you can afford one of those, I'd say go for it!