512MB of vram can only be useful for some kind of extreme modeler.
Say, a PIXAR 3D modeler, who probably makes models with an incredible amount of polygons that would never be seen in games. The texture resolution would most likely utilize the 512MB.
So, unless you plan to use your PC for that kind of extreme use, don't bother with it. Computer games will not see past 256MB of VRAM for at least another year. I have doubts UT 2007 will even use that much.
I do believe games like FEAR will be more processor-intensive since the physics and volumetric lighting is very harsh on CPUs. Remember that CPUs are the bottlenecks in games right now and that most of these video cards are not using 100% of their power. The only reason SLI is useful at the moment is because the data gets split into two 8X channels. Once the physics add-on cards are released CPUs will have a lot less calculations and single gfx cards will end up using all 16X bandwith.
A current 512 MB card will most likely be too slow when games that use that much vram come out. I almost bought a 256MB 9800 Pro which was released quite awhile ago. The 256MB was not even utilized until games like HL2 came out and in performance tests it did maybe 1-2 fps better. I think this was stated by my favorite review site toms hardware.
Read toms hardware. They usually have extremely accurate tests for any new technology. There should be a review on video cards with extreme VRAM amounts. I recall the conclusion stating that the extra $100-200 is not worth it in any way for normal consumers that game, video edit, photoshop, etc, etc
- Intel i7-930 CPU @ 3.4 GHz w/ Zalman CNPS 9900 MAX
- Asus P6X58D Mainboard
- Corsair 1000W PSU
- Cooler Master HAF 932 Adv. Chassis
- SSD Intel 40 gig
- HDD: 2x SATA III 300 GBs
- LG Blu-Ray 8X
- Gigabyte GTX 670 WF @ 1098 Mhz
- Corsair Dominator 6 GB (2 x 2 GB Trip mode)