Need video card advice

Hello folks, first of all I'm impressed by the add-on, needless to say, but this topic isn't exactly about that. FPS are horrible to say the least, it works a little bit but eventually CTDs, well the video card has been making problems since months already, giving artefacts, stripes and colored dots even just running the OS (Win7 64). FSX gives annoying 3D artefacts, either outside in the scenery or even inside the VC (very helpful). BSODs have happened occasionally, obviously I can't prove the card has been causing them but I certainly had such a thought. I know my sys isn't really that great but these are some basic specs: HP computer (don't know which one, at least not a gaming rig)C2Q Q8300 @ 2.5 GHz (not overclocked)8 GB RAM (at least something)750 GB HDD and then somenow... nVidia GF 7900 GS, 256 MB Alright, I'm sort of looking for a GTX 460 at 1GB for an update. Does that make any sense? If I upgrade, then I won't in a while afterwards, but I really don't want to spend hundreds here. What difference does it make which brand I choose, e. g. Palit, Gigabyte, Asus, Gainward, Zotac? There seems to be OC'ed ones as well but I really have no idea about OC'ing at all so I wouldn't bother much about that. Any thoughts or hints would be greatly appreciated, as I believe this is the bottleneck that make this simulation not exactly enjoyable as of yet.