I used a similar passive cooler to the main ones about now, not sure on name without pulling case apart now...
think it was a Accelero something or other
Sits on my Asus 8800GT in my Antec P182 case with good airflow
Normal Idle is 48
Load 60
Am in the UK, but is a really hot day today, card is helping run G-Force music visulisation (Very little load - almost same as idle) and temp is 58.
I would definitely go this route again soon on the next gen cards when they come soon as I Love a Quiet PC !
Am hoping they will be quiet enough for me not to have to bother though.
One word of warning, be sure that any after market cooler you buy will be compatable with your specific model of card.
My cooler would fit almost all 8800GT's except mine and to make it fit took a certain amount of carving away of cooler fins of the Accerlero Passive cooler to make room for a Asus nonstandard board cooler for minor components >_<
Basically is your card has the run of the mill cooling standard solution, and not a 2 slot extra size one, any normal aftermarket cooler should be fine
