That is a nice looking TV. I am not sure but I suspect that you cant use the PC (RGB) input to view DVD and Cable. The other way around (PC video on Component) will work if you have those connections on the video card and it outputs NTSC signal.
If that is the case, you will have to run one HDMI and one Component cable to the TV, somewhat negating the utility of the HDMI switching since you will have only the DVD signal going via HDMI, if that.
So why not get the RX-V2500 receiver (or any other without HDMI) instead and put the difference towards the speakers?
Cant comment on the Polks but also look at SVS, Axiom, AV123, Aperion, etc for speaker.