These are my specs.
Intel i7 2600K
AsusP8Z68-V Pro/Gen3
16GB Corsair Vengeance Blue 1600Mhz RAM @1.5v
HAF X RC-942 black full sized tower
Corsair HX1050
Corsair H80 Liquid Cooler
1x 240Gb OCZ Vertex 3 Sata 600
1x 1TB WD Caviar Black WDFAEX1002 Sata 600
LG SuperMulti Blue BH10LS30
Scythe Kaze Master Pro fan control KM03-BK
2x MSI n580GTX Lightning sli
Windows 7 Ultimate 64bit
This board is the best and easiest to use board, I've encountered so far. This board offers a lot of useful features for experienced and non experienced users. Plus, you can choose which features you want to install or not. The manual, also, offers a lot of helpful information for installation, configuration, and troubleshooting. As far as My SSD and my hard drive go. They are plugged into the Sata 6GB/s connectors, and function optimally. So far, I haven't experienced any performance problems with this system.
Next. The PCIe 3.0 devices will reach 2x's the speed, because the architecture is more effiecient.(32GB/s instead of 16GB/s)
You will be able to sli a PCIe 3.0 device.
The crossfire/sli set ups will function on the Maximus lV Gene-Z/Gen3 mainboard and the v series/Gen3 mainboards at x8/x8 like they do now, but again at twice the speed.
http://www.asus.com/Motherboards/Intel_Socket_1155/P8Z68V_PROGEN3/#specifications