Question: on a 4channel amp, can i run two channels at 2ohm and the other two channels at 4ohm?

Ok, as for the plan.. if so ^^^, i would get the PPI 5channel amp, which is 50w x4 @ 4ohms, 100x4 @ 2ohms, and 400x1 @ 2ohms. I could run the ID chameleon 2ohm components up front, and the 4ohm coax in rear...so 100wx2 for front, and 50x2 for rear. Then i was thinking maybe a single idq15 d4 ported off the 400x1 sub output? What other sub(s) would be good for that? If one sub, i'd like to go ported..if two, i could go ported if it doesnt require a lot of space...but would like to stay sealed. Any ideas? Going for a good mix of SQ and SPL.