also your system is top heavy. your cpu doesnt have enough grunt to handle 2 6850's by about %20...
your actually likely to get much smoother gaming with only 1 card.
i know you dont wanna hear that but to get the best from then 2 very good cards you would be wise to jump platofrm to an i5 2500k
for a list of games then you need the ati aplication profiler http://sites.amd.com/us/game/downloads/Pages/radeon_win7-64.aspx
(this is the win7 64bit version) just brows if you need a different o.s.