Levinson 380S with sub

You could use the record out but it would be a little cumbersome when changing inputs.

There seems to be both balanced and single-ended outputs.  I had hoped the single-ended output could be connected to a bass manager.

The record outs are only single ended.  Levinson does not recommend using the preamp balanced and single ended outputs at the same time (you would un-balance the signal by applying a different load to each phase).