My fans are cooler master R4 silent series 90cfm 2000RPM units. (not the sickleflow units, although they do have the same blades they have a different motor control system)
I have 4 rads with 6 fans per channel all running 6 fans per PA2. They draw .37A each at startup and spin from about 4.5v>12v. Under full RPM they draw 1.9A per channel. A lot of other fans out there are much less power hungry though, especially the 1850GT's. So you could run twice as many per channel and still be fine.
There's lots of useful data here> http://www.xbitlabs.com/articles/coo...oundup_18.html and also on skinny labs.