I just overclocked my 8800gs after installing the accelero x1 although that air cooler is not compatible with the videocard. I had to do a major modification to the cooler and finally got it on and I must say it was worth the 22 bucks and hassle.
stock cooler min 38 celsius max 71 celsius...
Pros: Performance increase
Cons: more money spent, single card works better than sli with most software,
Other thoughts: 8800gts is a great card, seems like an impulse buy for the two 9600gt's.
Hmm maybe, but i found a accelero x1 on a 8800gt by inno3d
http://www.inno3d.com/products/GRAPHIC_card/ichill/ichill_arcticcooling/i8800gt_ac_accelero_x1.htm
I ordered it anyways, got it for 22 bucks, if it doesn't fit i will find some way to mod it.