BT sound poor on most apps, okay during voice calls

[cattledogit]

My 6800 bluetooth sound quality is very poor when listening to audio files over my Plantronics 510 on any player and when using voice command, however the sound quality improves a lot during phone calls using the 510. By poor sound, I mean that the sound is so tinny that the notes in songs all sound the same and I can only distinguish the rhythms. Also, the volume is significantly lowered.

On my previous 6700's I always got good sound quality on this headset, so it's not a headset problem.

Device Information shows ROM version 3.08.666.1, and (stock) Radio version 3.42.02. PPCKitchen WM 6.1 20931 is installed with BT Quicklink, acbToggleBT, BT BPP, and PhoneWeaver's Today Plugin installed, among other apps.

Do I need to upgrade the Radio? I saw few of the reported improvements with radio upgrades on the 6700, and radio upgrades look more complicated on the 6800, apparently wiping out settings (?).