I am a service tech myself and u won't believe how many heat related problems (noisy system, system shut down with no reason) recently.....
to be honest, there is a very little u can do with a 40C temperature around. for example, I got a service call today from a elementary school, and not only the computer lab, but the main office (I guess the whole building) don't even have AC >< so you can imagine how noisy the CPU fan is no matter what replacement I give it :-(
my suggestion is use the system in a AC environment or in the basement (mine is pretty cold, especially with AC on in the house)
of course a better CPU fan, more circulation case, big heatsink will help a bit, but not a lot I am afraid with hot air around the PC... especially if you are overclocking....
well, maybe it is just those school .... I hope so.