I haven't tried any higher resolutions yet...I know my monitor can handle them though.
Even thinking to buy one 1GB now, and another one after the summer and put those in SLI. Or perhaps just go for 1 x 2GB.
if you want to crossfire in the future then i recommend the 2GB because when you crossfire the memory wont double, so if you have 2x 6950 1gb you would only have 1GB of VRAM to feed 2GPUs. if you get the 2gb version then you would have 2GB to feed 2 GPUs and that would be much better. especially in the future if your gonna play on higher resolutions.