If you are aiming to make a high qaulity 2D game, I don't think you should be scared of 100mb of VRAM. Steam's survey [>] is probably an okay way to see what a lot of PC gamers are using, only about 7% have 128mb or less VRAM. So unless you're making one of those mythical games that everyone can run (or a game for non-gamers), I think you'll be fine using 100mb or so of VRAM.