If you want ONE keyboard for normal stuff, and another for contemporary, I think most (if it's in their budget) would be better served by a workstation as the second keyboard.

Take a listen to the new Korg M3...... un-freakin'-believable!! Too expensive (though they DO have a module version)? Maybe a Karma, or MotifES Rack, Juno-G, etc., etc.. Most of these have the capability to grow more that the MM6.

But if you are on a tight budget, and play for the kids now and again, this might be the ticket.....!