oh... well if it's AGP I wouldn't spend too much... Maybe go for a 6600GT and OC... I'm using a cheap-o 6200 (got the none pipeline mod and a gpu lock, but it still runs surprisingly well for being a cheap place holder. Then again I went from a 9200 to it, soo you'll likely want something on par or above. From what I've heard, the x1600pro beats a 6600GT by a little bit... that said, what are the current prices on a 6800GS or 7600GT? you might be able to nab one for around $150... you can always be lucky and find $10 on the street.
EDIT: The most expensive 6800 on Newegg is $150.. other wise I think your right in looking at the x1600pro as the next bet... looks like you could try your luck and save $20-30 by getting a refurb.
Well anyway, good luck finding a card.
In The Mail!!!!- Athlon 64 3500 @Stock/Abit K9N SLi sAM2/2GB G.Skill DDR2 800 @Stock /XFX G7900GT XXX 520/1500Mhz/74GB Raptor w/ 16mbcache/300GB 16mbcache SATA HD/NEC DVD-RAM Burner/OCZ ModStream 520watt psu/ThermalTake Armor Jr./Logitech EX110 mouse/keyboard