6800GT upgrade?

I have a Geforce6800GT on an AGP motherboard.

What would be the fastest AGP NVidia card I could upgrade to and what sort of performance increase could I expect?

This could be the last time this PC gets an upgrade before I sling it on the trash heap and go PCI-E ;)

7800GS is the fastest agp card you can get.

Get a 7600. It's much cheaper, and I can't tell any difference between the two.

I'd probably save the money towards a pci/e upgrade and just put up with lower settings on games for now.