I bought a pair of those R50's for a buddies Xmas present. They sound ok, but remember that this series is either moth balled, or still down on the food chain as far as Polk goes.
But hey, I've heard them full range with an Infinity PS-12 sub, and an old Yammy DSP A1000. They will crank it out! I would only try the 30's up front if you can't get the 50's to image right.
But, budget permitting, keep those Polks, because they will make excellent surrounds if you buy something else for up front.