Frankly i think with a 6600GT you'll be bale to run it NEAR MAX. And really poeple that I talk to say it depends on the vaule of the ram. Now shadowing affects with a 6600gt would be as good. And I can see you beign able to run with max settings with 1 GB. 1 GB is a lot of memory even today. Frankly 1GB is ahead of the curve. Computer experts still say you'll be able to run games wiht 512 MB ram. However one day I might go 2 GBs.
Main Rig: I7 920 CPU, 6 Gigs ram 5870 GPU
M17X Laptop 2.8 Ghz Dual Core, 4870 Radeon