excuse me please, but why DivX may know why Vegas does not do such encoding? I know some programms do it, but some of they are illegal i heard. I thought it is mp3 issue, codec of mp3, maybe i must buy some?
Vegas will certainly render to mp3 at over 128K, I've done literally 1000s of mp3s at 192K. One trap though, Vegas doesn't support mono at over 128K unless you go into the Custom settings.
All that aside though I think there's plenty of DivX encoders out there, why not render to a DV AVI and then encode that using one of the many free DivX programs?
To be honest I can't find anyway in Vegas to render an avi file with mp3 audio.
What exactly are you trying to edit (specifically which codec) and what are you trying to render to (again which codec)?