i'm looking into the same thing.
What i figured out so far:
wi-fi bumps the price waaaaay up.
number of GPU's you can install:2-3 or 4 way SLI
ps i'm talking about the Z97boards here ( future SLI etc. compatible )
all the rest is just stuff that makes it look nice but doenst add much in the cost departement, most companies do it to get something extra, like better audio, some buttons, a colour her and there.
To give you an example, these are rougly the same:
- gigabyte UD3H, asrock extreme4, asus Z97-a
- gogabyte UD5H, asrock extreme 6, asus Z97-pro
and so on