IIRC, I was running the game @ 1600x1200 when it shipped, with most of the bells and whistles turned on (not all, though)--so you're jumping to some unwarranted conclusions about the efficacy of your present hardware, imo. (But I've been using AMD cpus since 1999 and AMD GPUs since 2002--when they were ATi.)

Always remember that software very often can seriously outpace the ability of the current hardware widely in use (as opposed to what's available) at its release--that's true, in fact, of any game that allows you to adjust things like screen resolution, FSAA, AF, etc. It's a good thing, too, because it makes the game software useful and enjoyable for years into the future--a decade or more, even.

Basically, I'd recommend either lowering the resolution and increasing the FSAA to the extent you can; or better yet simply turning off FSAA from the nVcpl and using something like FXAA, if available, instead--or no FSAA at all, either set in-game or through the nVcpl. If possible, turn your in-game shadow configuration down at least one notch, and lower the size of the textures through the in-game cpl. You could experiment with turning off vsync to see if that makes any performance difference for you. Basically, you should experiment with turning one in-game IQ feature off or down at a time until you reach the condition wherein both the IQ and the performance are to your liking, and *definitely* follow Hickory's advice about setting the nVcpl controls to "Application controlled" for this game, before you start changing IQ options. (Also like he said, you don't need triple buffering with your VRAM, either.)

If you want everything upped to max IQ in-game settings @ 1600x900, along with robust performance, you've no choice but to move up to more capable hardware--unless you are hobbled by a laptop in which you cannot upgrade the graphics device, then the good news is that for desktops you can buy something like a 2GB Radeon HD 7850 for ~$150 these days that will put you exactly where you want to be in the performance and IQ categories. As Hickory mentioned, these days anything less than 1GB VRAM is just not enough. As desktop resolutions continue to ratchet up in power over the next few years, towards 4k displays, products with even more VRAM are a sure thing. Depending on how you look at it though, the great thing about quality games is they do not *demand* you have the latest, most expensive hardware to play, because a quality game is a scalable game--that allows you to play even with older/weaker hardware. You just cannot turn on all the bells and whistles at your max, native res, though.