Well you can start by taking the DVD player off the top of the receiver, that should allow it to stay a lot cooler than it is at the moment. I wouldn't put anything on top of the receiver, you are just asking for trouble if you do that.

2xM80 VP180 2xQS8 2xM3 HSU STF3 LG 60PS11 Denon 3808 ATI 1506 LCR 2xATI 1502 Oppo BDP-83