I'm a huge fan of the
Plantronics Discovery 640.
Worked great with the 6700. It's probably one of the loudest BT headsets out there with great battery life and a relatively small size (it's exactly your first 2 knuckles on your pinkie, same width)
(
Big D5, don't bother with a2dp, open audio gateway, MSVC through headset, etc on the 700wx. Won't work. Either it's hardware limitation or a really lousy BT stack. Even Jetware Mobile cannot get it to work and they do magic with BT and PPCs
)