2k? a bit less to buy a graphics card.. not that you wont get it but very less retailers have AGP cards in stock... (those are old-style graphics cards that will work in your PC, new PCI-E wont work
)
bare minimum will be 6200 with 128 MB and 128 bit memory..
buy something like 6800xt with 128 MB ... will be best considering you have bit less to spare.. this will cost around 3800 new...
also better thing can be to look out for some good deals in the bazaar section of the forum *www.thinkdigit.com/forum/forumdisplay.php?f=56
and post your requirements in 'I want' sub-forum...
Also check wether you have AGP slot in your motherboard or not.. some only come with PCI slots...
good luck