The Antec VP450 is a super solid unit, and if you distribute the load correctly, it'll run without fault. I've owned one for 4 years, and I've abused the living crap out of it for 3 of its years, pushing nearly 500W at times through those two 12v/18a rails. I personally ran a massively overclocked and water cooled HD7950 (bios flashed to an HD 7970) off of my VP450 for 2 years, and that PSU has outlived my graphics card. A 750ti sips power more daintily than a stereotypical British granny at tea time compared to the 325W+ power draw I was demanding for my 7950. Even after all the abuse its been through, I permanently loaned it to a friend of mine, personally vouching for its reliability.
TL;DR: You'll be fine. Just use all the right power plugs, and be sure to use a surge protector. It's about as good a practice as using a condom.