I installed kb3 - so when I try to burn a CD in amarok, it opens kb3.

the problem is that it seems to only burn an audio CD from wav files - how do I get it to burn an audio CD from AAC and MP3 files, which is what I have?

I imagine that there must be plugins - can anyone tell me what they are and where I can get them?

Will

k3b uses ffmpeg as the default backend to encode to wav. Note that you must have ffmpeg installed and supporting lame and so on... IIRC k3b can use sox too.