Waitwaitwaitwait. This is the Sony DVP-S550D, that you're using, right?
RUN, don't walk, to your nearest Arcam dealer. Ask for a CD72 or CD62 (the only difference is you can't upgrade a CD62 to a CD92). Buy it. Take it home, plug it in, and realize how much your source sucked.
That's what I did. Before I got my Arcam I was using the exact same source. Trust me when I say it is in dire need of upgrading. The difference is night and day. The Arcam makes everything so much clearer and alive... When I heard the last movement of Dvorak's New World Symphony on the Arcam, I was sold. From that point until I could afford the Arcam, I had difficulty listening to the S550D.
The S550D is the major bottleneck in your system, if you like the 590s.
Next on the list would be to get the HD580s or HD600s with Cardas cable.