Well, I've listened carefully to the pc and found it is the whirring on the harddrives that make the most of the noise (just in case I grabbed those PABST fans )

The PC sits on the ground in a corner. Believe it or not, the PC is quiet for a monster with 4 fans (6 including the PSU) and 6 hard drives. I am just looking at decreasing the noise more. I already have a quiet CPU fan (a Zahlman CNPS6000-Cu ) and so now I'm moving to the other noisy components in the pc.