Will the 9400 Gt be able to run games like GTA IV on low or medium smoothly?

Ok, so recently my PCI E slot went bad so I’m stuck using the regular PCI slot. I don’t have a PCI card yet but I plan on ordering one online so I was looking online and the best one I could find was the EVGA 9400 GT (Here’s a link: http://www.newegg.com/Product/Product.aspx?Item=N82E16814130498&cm_re=EVGA_9400-_-14-130-498-_-Product)

Another question is would there be much of a difference if the card had the same specs but was PCI-E, PCI being older does it hinder a cards performance? Or can it run just the same?

PC Specs:
CPU 2.4 GHz dual core processor
Ram: 2 GB
HD: 300 GB
OS: Windows XP service pack 2
Power supp: 300W
For any other PC info please go here: http://www.tomsguide.com/us/hp-m7580n,review-810.html

Note: I have been able to run games like GTA IV smoothly on low/medium graphics with the 8500GT for the PCI-E I had but since thats gone, how well can it run with a PCI 9400 GT?

If you know of any other cards that are better for PCI please let me know.
Yea I was thinking about buying a new MB but to get a decent one is gonna cost quite a bit, I am on a very tight budget and I am trying to save up for a car so I can get a job and start paying for all this crap myself. Will it still be a significant improvement from on board video? I can only play games like WoW on low settings and on low settings everything looks glitchy and like crap on that game.