So I've been looking at this EVGA power supply it seems awsome great price fully modular but its not a single rail psu what do you guys think take a look here
There are only 20amps on each rail. I'd recommend at least 24 amps, especially if you are going to overclock or use a beefy GPU. It's doable, but there are better options.
Something like this would be great, and cheaper: http://www.scan.co.uk/products/650w-xfx-pro-series-core-edition-p1-650s-ukb9-85-eff-80-plus-bronze-sli-crossfire-eps-12v-fan-atx-v2
though, if you need modular, this Seasonic would also present a better option:
http://www.scan.co.uk/products/650w-seasonic-g-650-modular-80-plus-gold-120mm-silent-fan-eps-12v-quiet-fan-atx-psu