for the x16 slots, do you want them to run at full x16 for both slots or would x8 speeds be fine?
Also any sort of budget?
There is the
Maximus IV Extreme-Z which has 4 usb headers on the board and from the way I read it for the pcie it will do 2 of the slots at full x16 speeds
Yeah . . . that's a big-10-4, buddy. . . . It's a pricey board, even so . . . I see $359 at the Egg today.
I think you could compare this Maximus Extreme-Z to the P8Z68-V-Pro. You'll find that the SATA ports are the same, double the LAN ports (except for the Deluxe P8Z68), but the PCI-E X16 slots are more numerous on the Maximums with full x16(times 2) for SLI. I think you can get three-way SLI on this board.
There are some 8 USB2 and 2 USB3 ports, either at the I/O plate or in midboard. By comparison, the v-Pro has 6 and 2 respectively.
So the biggest difference I can see for a leap in price from maybe $210 to $359 is the SLI capability. [I'd look again to see if there's something else, but I couldn't find it the first go-around . . . ]
Heh . . . . again, a quick "take" -- I checked the review citations at the ASUS web-site for this Maximus Extreme-Z. These are the review cites on the Maximus product page. Of about 10 cites, 9 are reviews specific to the P8Z68-V-Pro, and one review for the Maximus Extreme-Z.
The PCI-E x16 slots come at a premium, and they crawfish onya with a lack of x1 slots. Depends on what you want to do, though. Personally, I just decided that SLI costs more in Kilowatts, and any one of the new "Fermi" and other graphics cards -- possibly but not exclusively working with the Z68 onboard iGPU -- offer "enough."
But as I said -- it's about "what you want to do." And it's nice to know you could take a V or V-PRo board, set up your whole system, pull it out six months later to drop in a Maximus Extreme-Z, and have little left to do to "update" your Windows installation, drivers etc.