Ozzy-
When you inserted the 3 xlrs to replace the Apex xlrs, what happened to the imaging? Depth of soundstage?
As far as digital vs analog, I would just try the P-4 on each and see what you think. Ideally, I would use 1 for each, assuming they work in your system. I'd also think about feeding your most important source with a P-4 from the Audience piece. It made a noticeable difference on my CD/SACD player.