Your current racks are pretty good. I think you may be able to work with them and not have to buy new. Here's 2 possible solutions for you. The first is to use the adjustments on your racks. If you are able to move the shelves up high enough, the shelf above the one you are moving up should block out everything but the face of the component. I know that may or may not work for you given any number of factors. The other thing you may want to try is Tls49's idea. I just noticed it. I was going to recommend something similar (Possibly get a piece of wood, or similar construction material, paint it black and cut it to the size of the entire opening on the shelf. Then put that behind the component. You would need to cut out the bottom portion of the piece you make to let the cables pass but if placed it very close to the rear of the component, you shouldn't see the cut out.). While my idea would work, I think it would be a lot easier to do it Tls49's way. Its just a much cleaner solution. Since your racks have open sides, it may also help to treat them with cloth as well.
I just thought of 1 last thing. If your MIT's are white, consider getting some cable dressing. (I think that's the correct term.) Its just flexible black plastic tubing with a cut in it lengthwise. It slips over the cable. It shouldn't have any effect on sound quality.
