you wont burn your gpu with silkroad unless you remove the heatsink/fan. When I used a 7600 gs I was able to have the highest settings possible minus the shadow detail to circle.
Heres what you should try. Try using the highest setting with shadows put to circle. If the games seems to lag/skip lower it to the middle settings. Keep trying till you have a good balance between quality to fps.
Compare to mine, I have 8800gt highest settings with shadow circle.
Hotan fps 9~15
Downwang pvp fps 25~70
Grinding fps 45~150
(to find out FPS (frames per second) use fraps free at
http://www.fraps.com)