"I currenrly have my DVR, my Xbox, and my reciever all in a stereo cabinet with a closed door. All work fine with no overheating. Is Sony trying to say that if I want to get a PS3 I need to buy a new stereo cabinet too?"
No, Sony is saying that you can get rid of everything else in the stereo cabinet, because remeber, the PS3 is an entertainment system, not a console