Media player primarily, CD player for unripped music.
Over the Christmas break I had a friend over and we did a test.
506.20 via coax and Mac Mini / Front Row via optical into 568.1
The mac used Apple lossless, set for bit perfect replay.
Two tracks set up to play at the same time and switched between the two.
We both could hardly tell a difference, any that was there couldn't be repeated and fast switching between tracks showed that we couldn't recognise or even guess what the source was with any success.
Steve.