The thing about the 80 x 38 fans is they generally have unbelievable flowrates (and they make a ton of noise). If you're looking for a no-holds-barred ultra-cooling setup, and can stand having a hair dryer run non-stop next to your head for hours at a time, the 80 x 38's like the Vantec Tornado or Delta EHE's are the ticket.
The 80 x 25's are the more common choice. With an SK-7, you could use a quiet-to-medium fan or an adjustable one, and probably get most of the overclock that the guy with the extreme-output fan is getting, but you don't live with a hairdryer in your room

If you're not going for a wild overclock and you want a one-speed fan that's quiet, get a Panaflo L1A 80mm 12-volt fan and you're in business.
