The most important airflow space you need to consider is behind the system. Don't put it in a cabinet or on a shelf that has a backing. If it does, cut out a small area so that the hot air can just freely flow into the rest of the room.
If you don't mind voiding your warranty, you can also greatly decrease the likelihood of the RROD by replacing the stock fan with a whisper max fan. Why? because this aftermarket fan is more effiecent and just a better fan than comes with the system, keeping it cooler than what comes out of the factory. The aftermarket fan also comes with a speed switch to change the fan speed. Even at default it flows air much better than the stock fan and at super speed your system will only be lukewarm even after an hour of play. One thing to keep in mind that this aftermarket fan had special "bonus" feature of little LEDs so that your system will lightup at its back creating a cool effect. I was slightly worried the LED contacts would hit the metal case and cause a short, so I wrapped the LEDs up with a thin layer of nonconductive tape. Not nessesary, but I'd recommend it just so that nothing could ever possibly happen.
As mentioned, do not bother with an intercooler. They don't do much to help as its an exterior product. It would be like having an air conditioner for your house located in your garage. There are some horror stories online, and while I don't think its a terrible choice to put an intercooler on your system, replacing the internal fan is simply a much better choice.
