Ok, just curious:
Is it worth the extra 100 dollars for the Lightning Xtreme 580 which has 3GB VRAM instead of 1.5GB VRAM?
It could be more future-proof, but it costs a lot.
Depends on the resolution you are running.
It'd be great for say 3 monitors running at least 1080p.
Remember, if you SLI 2 580s, the memory doesn't add up. Like, two 1.5GB 580s in SLI doesn't mean you have 3GB of VRAM, you can only use one instance of VRAM, so you still only have 1.5GB.
I'd recommend more VRAM for multi monitor, SLI or CF systems.