With a room that small, yeah, 5.25" speakers should do the job, unless you're not planning on having a decent subwoofer. Just make sure the the tweeters on all 5 speakers are pivoting in towards the listening area. Are you limited to in-wall, or is in-ceiling an option?
I've never heard Monoprice speakers, so I don't want to try recommending any in particular. Since it's for a home theater, I'd suggest going with higher end speakers with a good tweeter and decent crossover. 2-way should be fine though. Have you thought about going with Kevlar speakers?
- Brennan, Outdoor Speaker Depot