My XFX 6800GT seems to be running hotter than usual as it's in the 90's when I'm playing a demanding game like cs:s. I should also note that it's in the high 60's to 70's when it's idle, is this a problem?
Wow, that's high. Most I've seen for the 6800GTs are like in the mid to high 70's under load. But it does have a high tolerance for temp like in the 120 degrees Celsius range so you should be ok.
For 6800GT's I'm not sure how effective aftermarket cooling would be. They already have a pretty good and efficient cooler on them. Maybe get an exhaust blower and install it on a PCI slot right underneath the video card.
my friends 6800GT was running at about the same temps as u, even a little higher and it started to have problems (artifacts, freezing) so he got a good aftermarket cooler. His temps (under load) dropped somthing like 20C-30C.