Adding 2 JL Audio subs to my B&W 803 D3s made a significant difference.
Very happy.
For me, end game system.
Adding JL Dominion d-108 sub… surprise
No fan of subs. My experience, they muddy rather than enrich. New found appreciation for at least one in one of my systems.
Modest casita system: iPod, Luxman dock, Naim Atom set upon Quadraspire SVT stand, Puritan Labs P106 conditioner, Patrick Cullen shotgun copper cables and PC, ATC 7 speakers on massed stands and…. sub. Really fills in the bass and seems not to muddy. Breathes oxygen into the dynamics overall.