Hi all,
Looks like i'm the only one deploying 802.11ac at the moment!
well for the benefit of anybody else searching for the same thing, i managed to track down the best option for me at the time.
There doesn't appear to be any 3x3 USB devices ,i did find a heap of 2x2 devices but these all only supported USB 2.0 so they were bandwidth constrained at the USB port.
Trendnet appear to be the only vendor making a 2x2:2 device that supports USB 3.0. The TEW-805UB is the model i got. Not yet available in Australia but coming soon. I managed to import some from Canada without any fuss.
Hope that helps someone.
Scott