I updated to TC3.4 and tried mpd 0.16. I was able to use hw instead of plughw as device. Also, I was able to specify the format using
format "*:24_3:2"
Reportedly, mpd 0.16 and these settings permit passing of the sound stream by mpd directly to the hardware with minimal processing (also using mixer_type "hardware" to avoid software manipulation of volume). My initial impression is that the sound is cleaner and crisper. If there is interest, I can post my opinion after further critical listening.
Many thanks for your efforts.
As an aside, I am using gmpc as the client. The gmpc icons all appear as Xs. Has anyone else experienced this? Is there a dependency I'm missing? The only apps I have downloaded and installed are ntfs-3g (for external usb ntfs drive with music), mpd (this gets the alsa dependencies) and gmpc.