Have you considered upgrading with a motherboard with onboard GPU?? Not sure why your stuck on an AGP slot, but in the long run your better off with at least a PCI-e (v1.1 or 2.0) slot available for GPU upgrades. Your going to have a time finding a mobo with AGP/2 IDE slots. It can be done, but I think it's wasting your $. I'd consider getting a mobo with an onboard GPU, assuming your not gaming too much. AMD has some good mobo's with a decent onboard GPU (780g/790gx chipsets). They are about $70-120, depending on which one you get. Than just add CPU (60-100) and DDR2 (15-40 after MIR's). Than consider getting a faster HD for about $50-75 and your set! Intel has offerings too, so don't rule them out in this price range, their onboard GPU's aren't quite up to AMD offerings yet.
AMD 5000+/Asus 780g mobo - $125 shipped!!
2nd combo from the top!
Memory - $37 - $25 MIR = $12!!! Hard to beat 2 gb's for $12!!!
OCZ SLI-Ready 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory - Retail
HD (SATA saving IDE port for other optical drives, aka DVD's/CD's) - $55 shipped!! Fast and not too expensive!
Western Digital Caviar SE16 WD2500AAKS 250GB 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive - OEM
DVD Burner - $28 shipped!! Retail version shipped with software to read/burn DVD's. Also this would free up the single IDE port on the mobo for your existing HD's (assuming they are IDE too).
LITE-ON Black 20X DVD+R 8X DVD+RW 8X DVD+R DL 20X DVD-R 6X DVD-RW 12X DVD-RAM 16X DVD-ROM 48X CD-R 32X CD-RW 48X CD-ROM 2MB Cache SATA 20X DVD±R DVD Burner with LightScribe - Retail
If you opt to upgrade/change the DVD burner instead of the HD, than you'd save about $27 on the total below.
Total (CPU/Mobo/RAM/HD) =
$217 - $25 MIR's = $192!!! And if you drop the HD upgrade and insert the DVD burner above your total would be:
$190 - $25 MIR's = $165!!! Now I don't know what kind of graphics your looking for so if your a hard core gamer on AGP than that would change things up, but the 780g onboard GPU can easily handle WoW and similar games. It's up to you, but you'd be better off with a PCI-e slot than sticking with a dated and pretty much dead AGP slotted mobo.