Ok, maybe mpg321 doesn't work out of the box (it was just a suggestion) ... Another solution would be to convert the mp3's via xmms plugins to wav manually. This would mean you manually convert before to waw, and then burn the wav files.
If this is too much work, then I think you should just use mpg123 without worying too much. I still use it, and am not too worried because my computer isn't directly connected to the internet (it runs through another server/firewall), nor do I use mpg123 for much at all except converting mp3's sometimes.
I just tried myself with mpg321 and I can confirm it does not work :-/ ... Sorry, again, this was just a suggestion.