I find the Core i7 3960X so excessive even for a Dream PC,a Dream PC should be an incredible match BTW price/perfomance,if you watch the motherboards.org u've probably seen the system that won jerry over at BIOSTAR,a 10 000 BUCKS MACHINE! with dual MARS 2 cards,but at the end of the day they didn't stack up as he hoped,the config barely breaks 90FPS mark in battlefield 3 ( definatly a driver issue) and the 990x was a big bottlenekc for these cards,and the watercooling wasn't antec,or corsair or noctua no no no,it was a completely unknown brand ( i think FALCON),basically a total mess of money
A core i7 3930K unlocked CPU will do just fine,just OC it to 4.6 GHZ and u'll save about 500 dollars just for the same perfomance (overall it's the same both r 6 cores,but one is 500 dollars cheaper than the other)
You're totally wrong about the 7970,this card is not going to wake up neighbors (i got the point) it's newer 28nm architecture with up to 28Watts idle using 4 CARDS IN CROSSFIREX,the power efficiency=7970,also the geometrical processing unit has been totally remade,now it's so fast,Draw distance in games like GTA IV,HAWX2 is no more an issue with this 7 series of cards!
I think that two cards of these 7970,OCed more than 1GHZ on the core,can probably beat TWO MARS 2 (4XGTX580) in some scenarios!!!!!!!!!!!!
PSU is no less than 1050 platinum certification,or 1200 80PLUS GOLD,we know that 900W is enough for the system but unless it's 100% efficient i would worry so much about your system overpowering the PSU,you musn't cheap on the PSU,like a little overhead by buying an 80PLUS GOLD OR PLATINUM 1050+ Modular PSU from corsair or XFX :)
I think that you might want to add a couple of 7970s to the list.
Other than that u pretty much mastered the art!
Dream PC=Newer technology,no matter what u like it or not! (I personally plan on buying one of these they perfom very well)