I would definitely go with Enermax 80mm Fan.
Variable fan speed from 1000 -- 3000 rpm +/- 10%
Includes a gold grill for a nice appearance
80x80x25mm
39.8 CFM of Air
32.6 dba
Includes separate 3 Pin connector and optional 4 pin connector
You can change the speed of the fan by turning the knob. It's really cool, right now I have it at 2000rpm, but in the summer, I'm gonna change it to 3000rpm. It's really nice. Purple case and clear white fan with gold grill (which you can take off of course). Looks really nice and stays quite.
www.coolerguys.com has it for $9.95. My friend had Papst 12dB/20CFm 80mm fan, but he changed it to Enermax Fan.