If you are running an AGP system, you are most likely running PC3200 ram - Its not DDR2 or DDR3.
AGP itself only has a total throughput or bandwidth of 2133MB/s on AGP 3.0 compared to PCI-EX 4.0 which supports a total throughput of 16GT/s (Gigatransfers/s)
Even with PCI-Ex 2.0 its still 5GT/s which is leagues lightyears faster then AGP.
Long story short. the AGP system you are playing with is old and it wont turn into some monster rig by any miracle.
“I used to be a serial upgrader like you, then i took a downgrade to the knee” -FreedomEclipse