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.