I've really had to crack the books on this one but I'm becoming pretty convinced that the CAT5 cables DO offer a performance advantage. I've got a lot of data but here's a quick summation

1. Due to the skin effect the effective resistance of 12 AWG wires starts to go up around 5 Khz.
2. At 20 KHz the efective resistance of 12 AWG is about 43% more that at DC.
3. The 24 AWG wire is pretty much flat from DC-20Khz.(The skin depth is greater than radius of the wire)

What this means is that some of the higher frequencies and harmonics in your music are being attenuated more than the lower frequencies.

So I made up a CAT5 cable (16 strands of CAT5 which is just a little shy of 12 AWG) , hooked it up, threw in the Bob James Restless disk and yes there was a noticable difference in the clarity of the highs particularly on the sax. I'm going to play more with swapping things around to do more A-B testing, but I'm encouraged.

Disclaimer: Given the nature of the distortion I would think it could be effectively calibrated out by Audyssey or some other equalization system.