I have an Inspiron 537 with the graphics chip. What is the best compatible AGP card i can get for gaming?

My comp has the on-board graphics chip which is crappy. Its the Intel Celeron CPU 450 2.20GHz / 2.19 GHz. 64-bit OS. At the moment is has 2GB. I plan to double that or make it to 4GB. What is a good AGP card i can use in this?