By the time you dish out the money to get a 6800GT or 6800 ultra AGP, you're already close to getting a new PCI-E board and such. It's not worth overpaying for a 6800GT AGP that will cost you over $300 when you can get a PCI-E 6800GS, which is just as good for $200. See my point? You should just save up a little more for a PCI-E setup and believe me, you'll be happier in the end.
AMD 64 3200+ Newcastle@ 2.2Ghz
1GB (1x1GB) OCZ Performance Series
ATI X700 Pro 256MB OC\'d 475/525
OCZ Modstream 520W
Samsung 914v 19\" 12ms LCD
SB X-Fi w/ Logitech Z 5300e