From my perspective; I feel that it is pretty rare that any system will not benefit from a good dedicated sub. I love my Tempest sub in my system. My brother who listens to basically classical felt he probably won't benefit from a sub in his system. Which has Paradigm Ref. 80 speakers. Wrong! He said he couldn't believe how the sound filled in so much fuller with a sub. Of course the benefit is only realized with a good sub. I've heard many boomy boxes that make me cringe.
Morale of the story: A good sub will give you great benefits.