Since this is a dedicated theater, I would be looking at high efficiency theater speakers. You already have three excellent subs, so having towers is a waste because with a crossover their low extension is irrelevant. If you want to upgrade and get that dynamic, movie theater sound, then you need to look at brands like JTR, Pi, JBL, and Seaton.
I would recommend three JTR Noesis 228HT speakers for the front. These are very popular, have incredible dynamics, and will be a huge upgrade over your Polks. For surrounds, you don't need towersl I would grab four JBL 8320, these are THX certified and made to hang on the wall. You can put them in a more ideal location than your current surrounds, and they will offer the same great dynamic sound as the JTRs.
Samsung PN60F5300 | Denon AVR-1713 | EMP E55Ti | EMP E56Ci | EMP E5Bi | Outlaw Ultra-X12