I am NOT knowledgeable about this kind of stuff. But, I DO know, if the receiver's cooling vents are on the top of the receiver, having your CD player on top of it is NOT a good idea. Add in the fact that the receiver and CD player are in an enclosed area, and you have a classic scenario for an overheating problem. For sure, I would try rearranging before I made any other move. This, of course, assumes one can lock the wife in the closet long enough to get away with said rearranging and testing.
If the Cd player is sufficiently sturdy, you can place the receiver on top of it, assuming it will fit. That doesn't resolve the enclosed space problem, but it might be the first thing to try. If the wife continues to insist the components remain inside the cabinet, and if there is a back to the enclosed area, you might consider buying a small exhaust fan (similar to the one in a computer), cutting a hole in the back and mounting the fan in the hole to pull out the overheated air, thereby keeping things cooler.
But, the first thing to do is set up the receiver in open space and run it to see if overheating is, indeed, the problem.
