Lasereth

The memory doesn't matter to 95% of all PC gamers. Read my videocard buyer's guide (sticky at the top) for more information on how to purchase a videocard. The memory on the card is the last thing you should care about when buying a videocard. The actual chip in the videocard is what matters the most, not the memory. Then you find a price point you can deal with and find the absolute best performance out of a card up until the price point.

Your best bet is the GeForce 7900 GS or the Radeon X1950 XT on newegg.com. If you want to buy a videocard that will last years, then buy the GeForce 8800 GTS 320, but keep in mind that you won't see the power of the card unless you have an extremely fast CPU to go with it (Core 2 Duo performance). But when you do eventually buy a better CPU, the videocard will get even faster. The first two cards I mentioned will suit your CPU nicely (but probably still be slightly bottlenecked by it).

I'd also like to restate that the Geforce 8 series having DX10 shouldn't affect your decision to buy a GeForce 8 at all. These cards are supremely powerful regardless of their DX 10 capabilities.

__________________
"A Darwinian attacks his theory, seeking to find flaws. An ID believer defends his theory, seeking to conceal flaws." -Roger Ebert