If it were me, I would just take the back off the cabinet, (or cut large holes in be back), which would provide the necessary ventilation. I know that the XBOX 360 runs hot, and I would guess that the PS3 does too, (not even taking into account the amplifier). And you could buy one of the external fan units for the XBOX, (I use one), which provides additional cooling, (which would benefit the rest of the equipment, as it pushes the air around even more).
My two cents worth.%`òAGood Luck!
My two cents worth.%`òAGood Luck!