Cooler Master Haf-X
Asus p8p67 Pro
i5 2500k OCed to ~4.8
EVGA 9800 GTX+
G.Skill 2x4Gbs DDR3 1600
1 Optical drive
So it's time to upgrade the graphics card and I've scrapped together enough and I'm thinking about picking up 2 GTX 460 1Gbs right now because I'm confident my PSU can handle both of those. However if it's able to, I would prefer to either get a 560ti or maybe even a GTX 570 now and pick up a second around Christmas. Honestly I would prefer to not be cutting it super close and not really have any headroom so I'm content with the 2 460s if it would be too close on either of those later 2.
The HX 750 has plenty of power, it would have no problem running 2 GTX 570s with some overclocking, as long as you arent planning on a pair of GTX 580s, 5970s, or GTX 295s that you want to OC you have plenty of power.
I wouldn't feel comfortable putting two 570s together with just a 750w PSU. If I could give a suggestion, buy a 560, and use your GTX+ as a physx processor. It would give a meaty increase in framerates without needing to SLI anything.
750 watter is cool for SLI's 560's ....nVidia has certified numerous 650 watters for even twin 460's. With 570's and CPU / GFX overclocking, most would consider a 750 is a bit tight .... I'd want more headroom so as to main stable voltages (within 1% variation) under high OC's.
The following units get 10.0 ratings from jonnyguru.com
Antec SG-850 - $250
Antec CP-850 - $120
Corsair HX850 - $150 after $15 MIR
XFX Black Edition 850 - $130 after $20 MIR
I have used them all ..... of late though, only using the CP and the Blacks for obvious reasons.