Hi there,
Your solutions is to buy a NZXT INTERNAL USB EXPANSION (IU01) Kit.
I've recently bought a Rampage III Extreme and a Cooler Master 932 HAF, it was a bit late to realise that there were only 1 USB connector on the motherboard and two connectors for the case.
Did some research on the internet and found the NZXT INTERNAL USB EXPANSION (IU01) product.
It's basically an extension board, which allows you to plug in 3 USB 2.0 connectors and 2 USB ports and one single USB connector that plugs to your motherboard's front panel USB connector.
Have a look on the internet and you'll see what I mean, there are all the required parts in the kit and works like a charm.
Currenlt running a Rampage 3 Extreme with a 932 HAF casing and having all my front panel ports connected and working.
Cheers