I have the non sound units and 3 SD50s which run and pull fantastic. My BLI E7 runs decent but I have been having decoder problems and have had to remove the shell and reset the jumper a few times.
The P2K w/ QSI soung should be a better unit overall.
Turn the sound off and take a good listen to a BLI drive, most aren’t that smooth and quiet. But who runs them silent anyway.