Should I updgrade my mobo, processor, and vc, or just my vc?

Hello,

Asus P5N-E SLI (2 PCI E 16x slots)
Newegg.com - ASUS P5N-E SLI LGA 775 NVIDIA nForce 650i SLI ATX Intel Motherboard
Intel Core 2 Duo E4600 2.4 GHz
GeForce 7900 GT
3070 MB Ram

I want to upgrade my video to be able to play FF14 beta. I also want to run Starcraft 2 on really high settings. Do you have any suggestions? I was considering a "GeForce GTX 460 SuperClocked". It uses PCI-E 2.0. I am guessing my MOBO is PCI-E 1.0 because all it says is "PCI E 16x".

Would this card work with my current system? Would my cpu or mobo bottleneck the video badly?

Thanks!

Here is a link to the card I want