High-end iMac graphics upgrade?

Im looking to get my first Mac, and am looking at the 27 inch iMac with a 3.1 ghz core i5 and 6970m. I'm planning on doing a RAM upgrade myself, but I was wondering if it would be worth getting the graphics upgrade. I live in Massachusetts and if I order the stock config I can simply buy it off amazon or at a apple store in new Hampshire where I wouldn't have to pay the 120 sales tax. So is it worth paying essentially 200 for doubling the VRAM of the gpu if I'm only going to be playing games like SC2 Empire Total War, and other RTS's, M2TW and RTW?

I would try and find some benchmarks.

For games I wouldn't worry too much about the VRAM once you're over 512 MB.

Well, my suggestion is if you plan on eventually gaming with higher games, the upgrade may be worth it to future proof it a bit so to speak. Newer games are always coming out and they are usually power hungry.