I would say over the years the build quality of some polk speakers has gotten cheaper, my polk RTi 28's are much beefier compared to the RTI 4's for instance. My entire system except for my sub is Polk and I love the sound of them.
My dedicated theater room is only 1170 cubic feet and my system is currently 5.1.4, I think because of the small room I get away with just using an A/V receiver and not using separate amps which I personally think would be overkill for my Theater.