hmmm depends how you look at it...the Gecube X1950XT-T is the fastest...but the extra 5-7% over a X1950Pro doesn't justify it's considerably higher price...not to mention that the peltier is more trouble than it's worth.
I would say on Price vs Performance, the X1950Pro would be the best AGP card, I reccomend the Sapphire X1950Pro 512Mb AGP, I've had mine since the start of january and it hasn't given me a single problem and it's performance has been outstanding for an AGP card.
Nvidia wise that would be the XFX Geforce 7950GT 512mb, I can't really comment on that card at the moment because I haven't got my hands on one yet to play, how ever going off the performance of the Gainward Bliss 7800GS+ series which featured 7800GT, 7900GS and 7900GT GPU's instead of the regular 7800GS, it should have pretty decent performance and could be a good buy if it's price isn't much higher than the X1950Pro.
Unfortunately for the Gainward Bliss 7800GS+ series, I can't reccomend any of them becuase of their stupidly high price's (AU$550+) and rarity, only 1500 of each model was ever produced, and they weren't sold in the US.