9800GT is pretty much the same as an 8800GT, and back in the day, the best coolers for those were Accelero S1 & S2 or the Thermaltake Duorb. I had a couple 8800GT's with Duorbs and they cooled very well. Idle in the mid 30's and load in the mid 50's versus 80+ with crappy single slot stock cooler. You can overclock a lot more with them as well. You should be able to find either one in the $35-40 price range new. I think Microcenter still has the Accelero. Not sure where to find the Duorb. I bought mine from a forum member here.
EDIT: Yup, Microcenter still has the Accelero S1 rev 2 for $30.http://www.microcenter.com/single_product_results.phtml?product_id=0281555
Slap a couple fans on that thing and you should be good to go. The Duorbs cool about as well and have a smaller footprint though, plus they already have fans so you don't have to buy them additional.
EDIT 2: Here's a Duorb on eBay for pretty cheapEdited by c00lkatz - 4/17/11 at 5:35pm