I have a Levinson Reference No. 32 preamp (no longer in use, loaned to a friend). I use to use two outputs--one to the main two-channel amplifiers, the other went to an ambient sound synthesizer that fed four smaller speakers set up to the side and rear of the room.
That is a less common use than for subwoofers. Most linestages can accommodate two outputs--whether by having two sets of jacks or use of a splitter--and there should be no problems with significant sonic degradation.
That is a less common use than for subwoofers. Most linestages can accommodate two outputs--whether by having two sets of jacks or use of a splitter--and there should be no problems with significant sonic degradation.