It gets pretty hot inside the cabinet so was thinking of mounting some kind of fan above the receiver and xbox. Possible powering via the receiver, not sure what even exists for this.
I went with the dual 120mm fan kit from cool components. When ran at the 4 volt setting they are whisper quiet, and still move a lot of air. There is an off position on the power supply but is more convenient to trigger off your receiver.
They should be installed on the top rear of your cabinet(where the heat builds up). You should also have openings at the bottom front of your cab to draw in cool air. I'd recommend both fans exhausting air out wrather than push/pull config.