Psu, help with rails

Hello all, need some advice on how to properly power my gpu. I just updated my psu to a antec tp 750. My qeustion is, the psu is semi modular and has the main wires hard wired in with optionakl cables. Now i was reading that this psu in multiple rails with 25a each. Now should i use the hard wired cables to power my 6970 or should i power it using the optional modular cable which will be on a diffrerent rail? This my first high end card i have ever owned and im pretty surprised at the heat that it pumps out and im nervous about under powering it, thanks guys.

I would say that it doesn't really matter.
Looking at the specs, all the 12V rails are 25A. I wouldn't worry too much about considering if it's not able to draw enough current it probably won't work. So try it with the wired cables first, because for one it will also help with the cable management. And if it runs stable then great. If not, then switch to the optional modular cables.

The 12V lines are typically yellow. And unfortunately without physically opening the power supply, it will probably be difficult to tell which cables are on which rail. Especially considering you also have 12V lines going to your hard drives and cd drives. So if I were you, I would just try it with the wired cables and keep a close eye on is and see what happens.

Hope that helps!