''Or should i just bite the bullet and invest in a new motherboard with PCI-E slots....? ''
Ideally yes, buy a motherboard/cpu/ram bundle off ebay if you want.
The best AGP card is a 7950 Geforce. Which isn't great.
a Sapphire HD 4650 1GB DDR2 Dual DVI AGP Graphics Card for 62 pounds ????
Absolute rip off , unbelievable rip off actually.
a 6800gt is a good AGP card for about 15 - 20 pounds, or 7800 gs.