12-09-11: Mapman
The things I read that might make a predictable difference is choice of ic out, and nothing shocking there and maybe power supply but I would not expect much difference from that.
Mapman, I would suggest you give an upgraded, non-switching power supply a try. When I added a Bolder modded power supply to my Squeezbox 3, it made a very noticable improvement. Deeper, tighter bass and more extended, airy highs.