The best 40mm fan.

[HiJon89]

How about getting a 40 to 60mm adapter and putting a 60mm fan on...quieter and more cfm

That would block one if not both of his PCI-E slots, but if you can find some way to make it work that would be the best solution.
http://www.performance-pcs.com/catal...oducts_id=4352
http://www.performance-pcs.com/catal...oducts_id=3890