it;s not really that big of a deal, as long as the GPU runs without the cable and it doesn't lagg or freeze, you should be fine. What i recommend is getting a new PSU, like the Spire 600w, it has 2 PCI-e power cables. I have it and runs great on my Core 2 Quad rig, if you're interested, here are the specs:
Asus P5QL Pro Motherboard
Intel Core 2 Quad Q6700 @ 2,9GHz(Overclocked)
Asus GeForce 9600GT Silent Edition
16GB DDR2 800MHz RAM