matching in-ceiling speakers

hey i am looking to buy some polk rc80i speakers. I was wondering if i need to have all four of my speakers as polk rc80i's. Or can i go the path (like with floorstanding speakers) and buy my fronts as polk rc80i's and have the rears as cheaper speakers?

could i have the rears as polk rc60i's

also, i know very little about in ceiling speakers. Can these things handle top notch audio soruces