I will never ever buy ASUS motherboards again after the screwup I've got from them with the 350 € ASUS Striker Extreme II motherboard, two year and a half after I've bought it, and still they have not solved the hang issues (the damn motherboard is simply locking up now and then, even if your comp just stays idle in desktop).
As it has a 3 years guarantee, I think I'll try to return in and get it exchanged with some other motherboard, one for the new Sandybridges
Gigabytes UD4 is the same as UD5, while it costs with almost 100 € less: both motherboards will have their PCI express go down to 8x 8x with a 2 videocards SLI setup.
I7 2600k is worth the extra price even if only for the extra 2 MB L3 cache (which is the difference between 2 MB vs 1.35 MB L3 cache per core). Plus that with MG working on distributing the workloads on more cores, you'll never know..
Also, extra FPS over 60 is not a waste: some have high refresh rate LCD's (like me I have the 120 Hz Samsung 3D one), or want to go with 3D or/and surround resolutions (on 3 monitors) plus that you are not buying a processor just for now, you are actually investing in future games too, as you'll use it for at least another year.
580/590 are a waste of money atm: the best buy would be a GTX 560i with 2 GB VRAM, for almost half of the price of the 580. To which you can add another in SLI at anytime, a combo which would easily beat the 580, and maybe even the 590 too, and all of that while spending less money.