Compatible AGP Video Card & RAM for Asus P4SP MX?

I have a Asus P4SP MX Motherboard and Im planning to buy a video card and RAM to upgrade its performance. I know that my AGP supports 4x only but most of the video card available here are 8x, I was wondering if my motherboard can support a Ge Force 5500 or 5200 and can still function properly. Also, I have a 256 mb DDR400 RAM but some of the users I know uses DDR333, should I change my RAM to this or just upgrade my DDR400 to at least 1GB. Thanks a lot in Advance!