I have use OSS4 on a few machine and have been very satisfied, but not a
lot with multichannel. I appreciate the separate volume controls for each
application,

Maybe this could help:
http://manuals.opensound.com/developer/multichannel.html

Also, here's is some good information for supporting OSS (Although a little
old):
http://insanecoding.blogspot.com/2009/06/state-of-sound-in-linux-not-so-sorry.html

-Rich