UTP sucks as speaker wire. It's only 26ga .. roughly the size of three or four strands of a standard 12ga speaker cable.
There are adapters for A/V over utp. The typical unit has baseband video (composite) and two audio channels. The cost each is ~US$39.00 up to ~US$75.00, depending on the manufacturer.
Avaya/Lucent's model number is "380A." They also have a unit that is for RGB (should work OK for YPrPb component).
So, for about ~US$100.00 per end, you can use the 380A to pass your audio, and the RGB adapter to transmit the video.
I use the 380A to distribute A/V from a central satellite receiver. It works pretty well.
Good Luck
Scott