Single Rail vs. Multi Rail really doesn't matter on a well-designed PSU with properly defined OCP set points. The Enermax Modu87+ is such a PSU, and has received excellent competent technical reviews. The only shortcoming I see is that it only comes with two PCIE cables. You'd have to use adapters to power a pair of high-end GPUs. For the price, check out the Seasonic X-650 or X-750.