I’m using a Dell workstation with a Quadro FX 4500 and 8 GB of RAM and I have the same problem with both AE 7 and AE CS3. Save your money. If you don’t do much 3D, stick with gaming cards.
I do hope they figure this out one day, though considering the speed issues with both CS3 and AE7’s UI, I expect it’ll be a couple more versions before they get around to it.