All unnecessary, IMHO, due in small part to UnleashX!
Don't do the 12v fan mod, way too loud!
Don't do the 80mm fan mod - too much work for too little reward!
If you put a 7200rpm HD in there (size is irrelevant - and my wife agrees...hmmm...) then you can set the default fan speed in unleashX to whatever you want. I use 2x (=40%) as this is fine. If you have an *un-modified* bios, then it will stay at whatever you set when you play games etc. If you mod yr bios, then it will revert to yr bios default settings when you start a game.
So I use 4983 - unmodified - and set 2x for normal gaming, up it to 2.5x if it is a really hot day, or drop it ot 1.5x if I want to watch a DivX etc.
One of the great features of UnleashX (and now the latest XBMC has it too).