Of the cards you list, I would defiantly recommend the
Asus DirectCU II Top.
It has a custom PCB and heatsink along with a massive factory overclock.
In general, it performs the same as a stock GTX 680 and is virtually silent idle and load.
Asus GTX 670 DCU II Top Review
As a second option, the
Asus DirectCU II (non-Top) would be my recommendation.
While it shares the custom PCB and cooler, it misses out on the quite large factory overclock.
Personally, as the Top edition is only $10 more, I would get it.
The non-Top version is currently in stock though, which does count for something...
The other three cards you list all use nVidia's stock PCB and cooler.
As such, I would not expect them to be so very quiet or overclockable as either Asus card.
recon, I had thought that nVidia was finally at parody for Multi-Monitor gaming with AMD now?
I remember seeing in a few reviews that the GK104 is capable of driving all 4 display outputs simultaneously...