I can't imagine there is anything available that wouldn't degrade the sound. Have you tried tucking the wires underneath your carpet? How about hiding them behind the base board? If you want a really clean install, you could get some Niles plates and install them behind your rack and at each speaker point with your wires running through the attic and walls. This is a pain in the a$$ in existing homes but it's possible. Here's a link.

BTW, have you tried contacting your speaker manufacturer regarding your pushed-in dust cover? I've also heard of people sucking it out using something like a turkey baster and rigging some kind of cone on the tip of it. Really though, if you can't hear a difference I wouldn't screw with it too much for fear of making it worse.