I agree with MadAdmiral. Who cares what your system scores in a benchmark? It's real-world gaming performance that really matters. My work blocks inline images, so I can't see your screenshots.
A 5850 would game very well at your resolution. You don't have the option of adding another GTX 260 in SLI if this is your motherboard.http://www.newegg.com/Product/Product.aspx?Item=N82E16813130136&cm_re=MSI_Platinum-_-13-130-136-_-Product
The 790FX chipset supports Crossfire, but not SLI. If the system is not performing like you would like in games, I would sell your GTX 260 for as much as you can and pick up a 5850.