using 2 dedicated PSU cables is recommended since you may lose a bit of performance. Personally I use 1 psu PCIE cable for 1 card then if I have 2 cards then I use 2 cables. Using the same cable on both cards should make it "work" but you may not get the max performance.
Jay has a pretty good video showing it in action:
Hope this helps
BTW I'm not saying it wont work, most likely it will work just fine its just you may loose a few MHZ here and their but since ur PSU sounds good you should be fine