Two HD6790s or one HD6970?

I'm planning on upgrading my video card on my PC. Here's the specs:



Mobo: Asus M4A88TD-V

CPU: Liquid cooled AMD Phenom II X6 1100T

PSU: 650W

RAM: Corsair Vengeance 2x4gb

GPU: MSI GTX460



Two questions:



1. Would I get better performance running two XFX Radeon HD6790 (links below) with CrossfireX or would it be prudent to buy a single XFX Radeon HD6970?

(Two of these: http://www.newegg.com/Product/Product.aspx?Item=N82E16814150534 or this http://www.newegg.com/Product/Product.aspx?Item=N82E16814150517)



2. Is it particularly worth making this upgrade or should i be looking to invest closer to $400-$500? Basically I would like to run games such as Black Ops and Crysis 2 smooth as a baby's *** with most settings at high or ultra high, without getting outrageous temperatures in my GPU.



Its a very new computer that i just built so I haven't run a lot of graphically demanding software on it yet, however in anticipation of more very graphically demanding games I would like to have it ready.



Also, would I need a bigger PSU? I have a 650W that powers everything, which is DVD, mobo, HDD, 4 fans, liquid cooling on CPU, 2 cold cathode bulbs, and of course the video card.|||Two HD 6790s in Crossfire is a tad faster than a single HD 6970 2GB. Benchmarks: http://www.kitguru.net/components/graphi…



However, your board runs Crossfire in 16x / 4x. The 2nd card would suffer a performance hit from its PCI-E bandwidth being reduced to just 4x. If you're going to run dual-card configurations, you need to stick to a board that runs CF or SLI in either: 16x/16x, 16x/8x, or 8x/8x. Two HD 6790s in CF may be faster, but that's only if the cards are running at full 16x/16x or 8x/8x CF. On your particular board, the performance would probably be a tad slower than the HD 6970 2GB, due to the PCI-E 4x speed bottlenecking the second card. Yeah, just go with the HD 6970 2GB. It'll actually be faster on your board than 2x HD 6790s CF. No way I'd run CF or SLI on a board that does it in 16x/4x. If you want to CF, consider an AM3 board with the 890GX, 890FX, or 990FX chipset. Not the 880G chipset.|||you will always get better performance out of dual GPU's



If you want a Dual GPU solution, look at twin CFX(Crossfire) 6950's or a single GTX 580 for a non dual gpu.