There are at least two easy to try remedies.
1. The first reflection point is now occupied with the plasma screen. I would first try a blanket over the plasma. It does make a difference, how much it does is a matter of point of view.
2. The isolation for the CD player and digital gear might have changed. Try a wooden block under the CD player, and if it helps get a real isolation platform.
Also if you have added a power conditioner when you added the plasma TV, try plugging in directly to the wall and see if it makes any difference.