The Manager's highest OGG bit rate is 256Kb/s.

Plus, there's a bug in all current versions of Rio Music Manager whereby the Vorbis files it makes are out-of-spec if the codebooks take up more than one page (which they do at bitrates that high). FITNR.

If you're prepared to put up with 500kbits/s audio files, though, you should be encoding to Flac not Vorbis. (Unless you have a device that supports Vorbis but not Flac -- Karma certainly supports both.)

Peter