Need Help in Choosing Rear Speakers

I have the following speakers for my setup.


1. POLK CSI25 for center channel

2. POLK R50 for Front left and right.


For the rear and surrounds, I was planning on getting POLK R15. There is a good deal in Fry's for POLK R15. But there is a good deal on Infinity PRIMUS150 bookshelf speakers too. Hence, I am in dilemma now. which one would be better and match the overall setup? POLK R15 or Infinity Primus150?


Thanks in advance for your help.