Efficiency can be misleading. http://www.anandtech.com/show/2624/3
Short and sweet, they dont mean much if you arent running them to capacity, ie using most of the jiggawatts. 900 watt PSU running @ 2-300 watts is gonna be ~70-80% efficiency.
750 is usually more than fine unless you are running multiple GPUs or a dual GPU card (6990, 590, etc). Ive got 2x560 Tis running on my 750 with an overclocked i7 960, silent and not a single hiccup.
I thought you bought one forever ago when I sent you that amazon gift card you nub
proclaiming you are going to locate loads of ducks
<DaFox> When I was doing my sweaty shirtless crunches on a yoga mat today.........
<DaFox> My fat was making fart noises ;(