well - after hours of playing around, here's what I've concluded:
1: VLC will work in MediaTomb as a transcoder, but you need to set the sample rate to 22050 for normal playback of 2-channel audio. 44100 == half speed audio. seems weird to me.
2: Oppo will not play next audio file for transcoded audio. once it finishes a song, that's it. you need to manually select next song.
3: could not get ffmpeg transcoding to work at all.
4: ps3 mediaserver -- must transcode m4a (alac codec) to MP3. transcoding to PCM as this thread suggests doesn't work; end up with static. same results when playing back wav files.
5: the oppo handles mp3 fine. haven't tried high-bit rate mp3 yet.
6: asset runs under wine and also works, but audio only.
the oppo has a long way to go.
if they could support at least some lossless format that would be great. transcoding always blows as it's cpu intensive and youre ffwd/rwd is limited if it works at all.
needs support for mts/m2ts over dlna. my ps3 supports this. i'm sure the oppo can since it's rumored that from an AVCHD directory structure off of USB this will work.
on the other hand.....
i have a lot of SACD and DVD-A titles. and when they are available, will have BD-Audio titles. i'm ok with taking the time to put the disc into the player when i want to listen to the best quality possible.
so perhaps i'll set up a batch script which will convert my alac (apple lossless) to high-bit rate mp3 just for the oppo. disk space is cheap