I'm sure some of you have seen these but for anyone else, rubber grommets, the best solution: http://www.frozencpu.com/cgi-bin/frozencpu/scr-10.html At $0.60 a pop ($2.40 / fan) these are pricey, but a quick search could yield some better prices, somewhat hard though considering most people want you...

I saw this thread after making a purchase from these guys. Should be coming by end of the week. I'll tell you how it works. I got: 9 sq.ft. of 1/8" mass loaded vinyl. 1 lb/sqft. 12 sq.ft. of 1/8" closed cell foam. Came to about $50 with shipping. I thought this was a great price, considering dynamat...