ok first of all wtf is up with all these posts talking about voiding your warranty? you'd have to be the world's biggest idiot to think that opening your 360 (or any other console, or almost every consumer product available) will NOT void the warranty. we all know it will, so if anyone is reading this and thinking about performing the mod, they'll be aware of the consequences if it goes belly-up.
glad i got that off my chest.
second of all, i'm wondering about these extra fans stuck on the outside of the case - i'm assuming the two internal fans are still functioning as well? if these fans are spinning and sucking extra air out, wouldn't that cause the two internal fans to spin faster? if so, wouldn't that create some excess voltage (spinning converting into electricity)? i'd assume that that would only be the case if they were running at full speed (12v) to begin with, though.
may do this thermal mod, and possibly get some ramsinks too. i've already opened my 360 to get at the drive to repair a faulty premium that was also out of warranty (before i learned about the whole firmware encryption thingy) so my warranty is void anyway (and the back doesn't look too hot as it was the first 360 i opened and had a helluva time with the tabs!)