Honestly now days i dont think the response is that much difference because of the advances in motor technology. You could go with a 12 and be ok. To anwser your other question yea it would be possible. The way i would prolly do it would be to hook a switch to the remote line for each amp.
Alpine R types provide a good balance between SPL and SQ, and sound good, shine even, when listening to trash metal type of music. I have a pair of 12's myself.