This card supports AGP 2.0,which is AGP 4x so your slot should support it.
AGP pro as used by Asus gives backwards compatibility with AGP 1x which most AGP 2.0 slots didn't.
I wouldn't use a PCI slot card unless absoluely necessary...they run much slower than through the AGP slot so might not be an improvement on what you already have,but if you do need to use one
You didn't say what you want to use the new graphics card for or the speed/type of cpu and memory you have so it's more difficult to match a card to your pc.
Both cards I've mentioned are bottom of the current market cards but should be better than what you already have.