Forgive me if someone already said this, but I just skimmed through this thread.
The amp is not going to cause the air to get hotter than it is. If the amp is cool, then it's not the issue.
My theory is that the PS3 is getting warmer because you've put it in a smaller space. If I remember correctly, you raised the shelf to accomodate the Rotel, which would reduce the space around the PS3.
So, if the amp really is cool, I'd focus your cooling efforts on the top shelf where the PS3 is located.