The Prime family can be easily driven with any quality AVR. The above recommendation for the X4000 (or anything in the current 4000 series - 4100, 4200) is very solid.
We prefer Denon and Marantz because they use Audyssey (look for MultEQ XT or XT32 as the type). External power is typically not needed, but if you have a very large room, sit far from the speakers and like to play the system at theater-like levels, then additional clean power (especially on the front stage) could be a good idea. Hard to beat Emotiva in that department - the XPA-3 is super popular for the LCR and then let the AVR power the rest.
If you think external power might be in your future, just make sure the AVR has pre-outs for most of the speaker channels. It's an increasingly rare feature these days, even in mid-priced units.