I recently got a samsung 305T and my 8800GTS 320 just doesn't get the job done. After seeing the results posted by the GTX 280 at 2560X1600 being tied with the GX2 I don't know what to get. One one hand the GTX will probably improve with drivers but the GX2 can be had for ~100-150 less. Also getting 2X8800GT (159 each) or 2X8800GTS 512 (~240 each ) is an option since I already have an SLI mobo.
System Spec: Samsung 305T Q6600 @ 3.6GHz Striker II Formula 780i 6GB Corsair DDR2 800 8800GTS 320