I got a Hercules Prophet II MX, and at first it seemed to work great, especially in OpenGL games like QuakeIII. Then I decided to benchmark it with 3DMark 2000 and it performed horribly. I later found out why - all GeForce2 cards are AGP 2.0 compatible and my motherboard was only AGP 1.0...
Just so that you don't make the same mistake I did. Also if you're getting a MX card, I'd go with the Hercules.