Well if you don't need the SATA III (well want it - only like one SSD supports SATA III right now xP) then you can go with the USB3. IT's pretty much the same board just no SATA III. And for $109 it's not bad x). There are no hard drives out there that can take advantage of SATA III - so it's not a critical requirement, just a "want" lol.
Yup everything should work fine
The wireless will fit in the second PCIe - of course it'll only go about 4x - but its not a graphics card so that overkill speed already xD
Btw, what are you looking into for the psu and memory?