At this point I would get a highly OCable gtx 680.
Depending on the benchmark:
The 6990 (or lower clocked 6970 crossfire) is quite a bit better.
Don't know what these power and noise issues are, it all depends on which card. 650w of power draw (un-overvolted) is great.
The 680 needs a good bit of oc, I'm guessing 1450mhz plus to match a 6990, though that isn't a guarantee. personally at this point i would go with the fancy new cards. I don't believe this microstutter issue, there are a few articles that go indepth on it, I've never faced it myself, though my array of games is limited. You will max everything on 1080p at atleast 40fps though if you go with the 6970s. And a good few clock to 1000+ on the core like mine do.
Most will give you 60fps maxed btw, the exceptions being BF3 with MSAA, does not work on AMD cards to my knowledge and Witcher 2 with ubersampling, the 40fps average on my highest oc's, 1050mhz/1500mhz (core/memory), significant overvolting, 3.8ghz i7 930 @ 1080p, though that game is the most intensive that i know of except for Metro with DoF on.
I'd say the 680 at this point, but I love my cards. They still don't max everything I wish they would, but no single card solution I want could do that.
edit: As being both an SLI and Crossfire owner at this point, I do not intend to ever get two cards again. Profiles can be annoying, from both companies, and cfx/sli is not always supported. The performance boost is great though, but hopefully by the time the next gen comes around, even the witcher 2 EE will be maxed by a single card, or atleast I hope so. And watercooling is limited, as you have to purchase for a second card and increase your rad amount. This doesn't hold true for everyone, I'm just saying I personally will try not to use two cards from now on.
Both are good options, 6970 tris only scale well at multi monitor resolutions, triple scales poorly for everything under 1440p.TL:DR gtx 680 for now, though the 6970 is a great option, power draw for both is minimal, both play games at great frame rates, both scale well in dual cards, and microstutter is on a person to person basis.Edited by Spykerv - 5/3/12 at 12:49am