I'm not sure about the 7970GE but the custom 670 I'm running is extremely quiet - basically silent at idle and a whisper at load.
Even a GTX 660 Ti with a custom cooler isn't particularly quiet and that's going to be quieter than any GTX 670 unless it's running a water cooler with a huge radiator with a large slow fan.
http://www.anandtech.com/show/6159/the-geforce-gtx-660-ti-review/18
From looking at the design of the Xbox One, I'm willing to bet that Microsoft is aiming to hit near the noise floor at the Anandtech labs. As well as going completely passive and hitting well under the Anandtech noise floor when not gaming.
To accomplish anything like that with powerful PC hardware will require watercooling with the aforementioned large radiator + large slow fan.
Perhaps, I'm wrong, however, and Microsoft isn't aiming this directly at home entertainment enthusiasts where you often have to spend over a thousand USD for a truly quiet HTPC suitable for a well designed home theater room. None of the cheap and often noisy components that are being bandied about this thread. We're generally talking full passively cooled systems or systems with at most one fan. But even one fan is often too noisy for a real home theater room. As the fan can be quite obvious during low noise moments in film.
For gaming a little fan noise can be tolerated in such conditions, hence, my speculation that the fan in the Xbox One will only activate during gaming.
Taking note of that, it's particularly noticeable that they went with something similar in specs to a 7770 but with the clocks of a 7750. As the 7750 is currently the most powerful passively cooled GPU you can get at retail. Speaking of which those passively cooled 7750's are still over 100 USD while almost all of the actively cooled version are under 100 USD. Just goes to show that a good cooling solution that isn't always reliant on active cooling is more expensive to design and implement than an active system.
I'm going to guess significant resources have gone into the Xbox Ones cooling system with an eye towards quietness.
This next bit isn't a reply to your post, I just didn't feel like posting another post.
But I like how desperately some of the PC people are trying to make PC hardware seem as affordable as the next gen console hardware is (software is another story entirely). Resorting to used hardware? Really? Resorting to cheap components?
Sure you may be able to approach the performance of the next gen consoles (doubtful due to the lower OS overhead, tighter integration, ability for developers to optimize for basically one hardware target, etc), but at a significant loss in user experience, ease of use, quality, reliability (used hardware? cheap hardware?), etc.
And I'm one that does almost all of my gaming on PC still, and that will likely continue during the next gen unless FPS games start to support keyboard and mouse on consoles.
You pay more but you also get more functionality from a PC. It's certainly not relevant to gaming, but it is still part of the cost benefit. Just like Xbox One will cost more than the PS3 and that cost may or may not be justified depending on how much one values the non-gaming experience.
Personally, I spend quite a bit on my PC. Then again I also use my PC for work. If I didn't, I'd be torn as to whether to start doing the majority of my gaming on consoles. Probably not, as I can easily afford the cost of a PC. But for many people it's a quite valid choice that they make for affordable gaming.
Regards,
SB