Since they are rushing the 680 out I predict it will be more alike the 480 in heat and noise, the 580 was an improved version of 480 (what it would have been if they hadn't rushed it).
It will come out April 12th, I don't think it's rushed.
... I expect the heat output of a stock 680 to be every bit as enormous as the 580 before it. In other words, aftermarket cooling (such as the Accelero attached to this 580: http://www.newegg.com/Product/Product.a ... 6814162073
) is the only way to have a chance at a relatively-quiet system, and internal coolers like that require good case airflow.
The Tahiti core (HD 79X0 ) has 4,3 billion transistors @ 925 Mhz max. The GK 110 core (GTX 680/670/660TI) has 6,2 billion transistors at 850 Mhz max. .The 7970 uses 295W at Furmark with 3GB of memory. The 680 has a bigger core, slightly lower cloacks and 2 GB of memory, both cards' memory is clocked at 1375Mhz, or 5500 Mhz in marketiong speech.
The GTX comes in at 320W Furmark. I would expect the 680 to consume about 15% more: 360W Furmark, 265W in Games. In the past the have power consumption has gone up roughly about 15% per generation. I will plan the purchase of a my new PSU accordingly.
All of this is speculation at this point, so take it with a grain (or heap) of salt, but I have followed the rumors closely.
A good aftermarket cooler will be a must have item. You will also need a well ventilated case.
Further complicating things is that I've developed an affection for Micro ATX cases. This system will visit LAN parties occasionally so the smaller size will make it easier to handle. I'm willing to give up on this, though.
The TJ-08E looks good, and is well ventilated.
The Fractal Design and Define Mini is dampened, but may need more than the standard vetilation.
The Fractal Design Arc Mini and Core 1000 are more open, which is better for ventilation, but worse for noise.
Bitfenix will bring a new line of cases including an interesting Micro ATX and ITX case, they should be out before the new graphic cards.
The Xigmatek Gigas
is new Mini ATX cube. It's bigger than other cubes, made from aluminum and comes with 4 120mm fans. No reviews yet, shoub be in stores in march.
Lian Li has a series of cube cases: the PC-V 35x. They are alimium, too, but the 120mmm fans are a little loud.