I have a 5870 also and it runs great .
download the shadows lite mod and put slider half way .
http://www.filefront.com/17018577/Sh...ent%20ModLR.7z
In the catalyst control centre use Multi sample AA for the AA mode . Filter mode is box .
use antilag
http://www.subsim.com/radioroom/down...o=file&id=2871
do not use the mod enebler to enable the antilag . Instead place the 2 extracted files
in your main Sh5 game folder .
check out this thread
http://www.subsim.com/radioroom/showthread.php?t=192374