You appear to be eyeing a Monoprice-only set-up. Given that, IMO:
1. Go with the 10" sub.
2. Get two pairs of these speakers
for your L-C-R (and keep the fourth as a spare).
3. Get a pair of these speakers
for in-ceiling surround duty.
4. It's not a dumb idea, but it may not be necessary in your space. Wire for 7.1, start with 5.1 speakers and, if it you find it's really not enough, just add two more speakers later on.
-- Edit --
Regarding points 3 & 4: If you're stuck on using the MP center channel speaker - which has 5-1/4" drivers - IMO you should go with matching speakers with 5-1/4" drivers for L&R, in order to maintain consistency across your front three speakers. In that case, you might as well go with 5-1/4" speakers for your surrounds, too.