Now that some music download sites are producing high quality downloads requiring a wma9dmo codec, is there any way to add that format to the music I play with amarok?

URL of some of those sites would help to test it out ...

Here you are:

mms://87.98.222.178/CLASSICROCK

and more on http://miastomuzyki.pl - it's in Polish, but click on any channel name to get a list of streams

Best,
J.