I decided to try the Motorola HT820. Paired easily with my 6601. After the initial pairing, automatically re-connects both with both Headset/handsfree and A2DP profile--the 1st headset of the 4 I have tried that automatically re-connects the A2DP High Quality Audio profile.
Audio quality is also better than any other BT headset I have tried. (I can now notice the differences in quality between a 24k and a 64k stream, for example.)
Call quality is also good--much more clear than anything else I have tried.
Connection is maintained for about 8 to 9 meters through a wall, which I have not experienced with any other BT headset. I can walk around with the 6601 in my pocket while streaming audio over Vision without any pauses or dropouts, which is another first.All audio controls work with both Windows Media Player 9, and with TCPMP Version 0.71k.
The BT820 is noticeably heavier than the clip type BT headsets--I suspect that it has a significantly larger battery than other headsets, as the battery life is much longer. I also can't help wondering whether the extra weight is a factor in the noticeably better performance.
On the downside, it is a non-adjustable neckband style headset, which means it either fits or it doesn't. I can just barely get it to fit my 7 3/8 size head, and have worn it up to 2 hours with no problem.
In sum, it's the best-performing and easiest to use of the BT headsets I have tried (which includes the i.tech Clip S, the C&C BT Mini Stereo, and the GlobalSat BTH-820). The only real issue is that the neckband style is not as comfortable as the more traditional over the head style headset.
One feature that I like and have not seen on any other BT headset is the ability to turn off the indicator lights.
Mick