I bought a pair of these
http://www.ebay.com.au/itm/BT-interphone-Bluetooth-Motorbike-Motorcycle-helmet-intercom-Headset-500M-Black-/321832490992?hash=item4aeeb617f0 off eBay around five or six years ago, and found them pretty good.
I suffer badly from wind noise and buffeting, and wear (insert?) earplugs whilst riding. The BT unit's volume was adequate even with the earplugs. One time on the Calder Freeway sitting around 110m/h (Mmmmm.....may have been a bit faster), sitting behind the ST13's raised screen, I took a call on the mobile and could hear the caller (no. 1 son) very clearly. When I said I had to terminate the call because was doing 110km/h on the bike, he said that he had no idea, the reception was crystal clear.
Anyway, the BT's bit the dust, I think I cooked the battery on one through charging with wrong charger. I bought a replacement, and then another one bit the dust - sometimes I'm a slow learner.
I now have a pair of Sena 20S, thanks to Father Xmas and Mrs W. These are much better, and the in-built FM radio and voice-activated intercom are real bonuses.
If you are interested, I reckon I could scrounge enough pieces for one good unit for you to try.