If you are running vista, it's likely that your graphics are on the cpu as a shared process. THis is common with vista machines.
YOu will need to be careful in buying a graphics card.
nvidia cards for next gen games need to be at least 800 series to play pretty much any of them. an 8800 gt or an 8800 ultra will rock your gaming world
vram is insignificant, no gaming company produces threads that will use more than 256 m of vram. There are no games that use a 512 chip and 725 chips are overboard and a waste.
It's al about shader models, vertices and bus speeds.
ati or nvidia cards are best when in the over 600 series and watch out for suffixes like LE SE etc. XT is good but only if the card is a 600 or higher in the ati series.
in nvidia, 7800, 8600,8800 and higher cards will be good for at least another year or two.
your main problem is goin to be vista which still has many drivers issues and has a tendency to assume that everything should be cpu bound.
oddly enough, you can thank flight sim x for that little tidbit.
here's a list i more or less agree with
http://internetgames.about.com/od/hardw ... ocards.htm
Coconuts. Bananas. Mangos. Rice. Beans. Water. It's good.