1: PCI-E's are New
2: obvioulsy newer is better, as in case you buy a PCI-E card, it will be used in upcoming boards as well, whilst AGP will have limitations. as if you see market trend, every new motherboard chiupset is coming out with PCI-E slots.
3: theorotically, PCI-E is twice as fast as AGP (previous tech for Graphic cards), but in actual it isnt. same goes to when AHP 8X came out, it was marginally faster than AGP4X, so is the case with PCI-E. i'll recommend this as the cards bought on PCI-E can be used in future as well.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"