Originally Posted by stangs
Ya I wasn't gonna get the 850w the reason I went with it was I got it for 130$ on sale so figured what the heck and eventually I am wanting to crossfire.
Oh, then here is a better PSU for less:
650W Rosewill CAPSTONE Modular Cable Version Series for $89.99 shipped, $74.99 after $15.00 rebate card
It has way more than enough power:
With one 7870 under full load in their system, their PSU pulled 274W. The 7870 alone pulled 127W, so I'll add 127W to 274W in order to figure out a crossfire power draw. That would make the PSU pulling 401W from the wall outlet. Their CPU was idling, so if I had 150W for a 3770K overclocked to 5 GHz and under full load (I can prove it), then that makes the PSU pulling 551W from the wall outlet. So if the PSU is 85% efficient while pulling 551W from the wall outlet, then the system is pulling 468W from the PSU. However, the gaming load would be closer to 375-425W - maybe 450W at times (maybe).
So with the extreme situation where the 7870s and the overclocked 3770K at 5 GHz are under full load simultaneously, the system could pull up to about 470W. A more realistic power draw would max at at 425W to maybe 450W. This means a quality-made 550W power supply is more than enough because the PSU would be able to continuously deliver 550W if it's ever needed. This isn't cutting it close, it's more like the sweet spot. ;)
However, a 550W PSU that has 4 x PCI-E cables costs more than a 650W with 4 x PCI-E cables. I mean for example, here's the cheapest 550W unit I can find that has 4 x PCI-E cables:
550W KINGWIN Absolute Platinum Series for $124.98 after shipping, but it's not even modular.
Here's a similar modular unit:
550W KINGWIN Lazer Platinum for $154.98 after shipping
So yeah, the Rosewill 650-M is a "no-brainer". ;)