I'm looking to build a new core2duo system (E6600). I currently have an eVGA 7600 GT card and was wondering which of the following would be a better option: SLI a second 7600 GT ($130 more) or purchase a midrange card (7950 GT or thereabouts, around $250). This would be going on an Asus P5N-E SLI board assuming I go with SLI.