Low volume levels from CDs that were burned on the BR-900CD are usually due to lower mixdown levels when Bouncing and/or Mastering. In the BR-900, look at the “L R” level while Bouncing and Mastering and be sure that the meter is averaging as close to 0dB as possible--without going over and distorting.
If the meter is averaging around -24, rebounce and/or remaster the song(s) with the “L R” meter level higher. This can be accomplished by raising the individual track faders and/or raising the MASTER fader when Bouncing and Mastering. This will allow the hottest volume levels possible to be burned to CDs.