check this out...
http://www.driverheaven.net/reviews/Sapphire%20X1950Pro%20AGP/index.phpa review of an AGP card based on new technology. its not directx 10, but its atleast good enough to stick in your agp slot!
DH Review: Sapphire X1950 Pro 512Mb AGP
there is also a new one that i seen this morning - a 1600 and x1650 in agp flavor.
as for ati vs nvidia - i dont think thats an issue at all.
you might want to try
http://www.drivercleaner.net/ im not sure if it cost anything anymore - but it didnt before - if you cant find a free version on his site - download an older version which is free elsewhere. - i havent used this application for a while because i just formatted my system.
here is ati's new offering.
http://www.theinquirer.net/default.aspx?article=36642it looks promissing! but we may have annother delay on it!
http://www.theinquirer.net/default.aspx?article=36673i dont think the top end for that chip will be agp at all, but within some months we will likly see a midrange one with agp.