IMO, there won't be any audible difference at audio frequencies between Cat5 & Cat6. The audio "preference" is to use plenum rated as the conductor insulation is specified to be Teflon, versus high-density polyolefin for risers and general purpose. But, again, on short runs probably not a significant difference.
In the past I did some 10', (3m) speaker wire pairs plaiting the twisted pairs. There were 8 pairs per channel. To my ears, there was better sound staging, low level detail and timbre with the plenum rated Cat5, (teflon). Fun project but it took a very long time for my fingers to forgive me.
Cheers,
Geary