Of course I'm gonna try these keyboards first, but since I'm not familiar with midi, I first wanted to know if I can combine these two keyboards. For example, can I play the piano on the A90EX (the Roland sound in this case) on the right part, while on the left part, I play the chords that will control the styles on my GEM?
I know I have to hear and feel it myself, but is someone willing to give his opinion about the sound and feeling of some controller/master keyboards or synthesizers?

I'm still interested, so for me, my question isn't useless at all...

Thanks!