Really its a combination of both. I have a 5830 that sits under a desk that I burnt the stock fan out of within a year (running at 100% all the time is never a good idea). I then strapped a delta 120 on it and it did its thing. Yes, noisy but yet. That eventually died. Now I have a delta 92 on it. Still does the trick at keeping it around mid 70s and is less noisy than the 120.
The delta fan blew out??? I thought they lasted forever. I run the delta at around 80%, I'd rather replace the case fan, then replace the gpu fans.