Okay youngins I'm gonna explain this to the poor guy, as you are confuseing the hell out of even me.
So it would seem that you have both PCI and AGP slots on your motherboard, but NOT! a PCI-E. Since you dont have that lane, disregrad anything refering to a PCI-E card above mentioned.
Currently there are a range of good cards from ATi and nVidia that support AGP.
ATi's 9x series, the whole X6/7/8/85 series, and the X1600 / X1800GTO all come in AGP.
nVidia's whole 6 series, and the 7800GS come in AGP. No other 7 series cards are AGP, due to manufacutes trying to sway the market to PCI-E.
Out of all these cards, personally I would buy a ATi X800GTO / GT, or an nVidia 6800XT. Both cards will run about $180, and serve you very well, until you have to upgrade for DX10. True you could spend more, however you may as well take the $250 your going to spend on a 7800GS, and use it to buy a decent $70 PCI-E motherboard, and a good PCI-E card. As for where to go,
Once you Know, you newegg. Newegg.com has by far the best selection of parts around, and by far some of the cheapest prices I have ever seen.
Cheers
Cameron