Nick, your premise about the bigger sub sounding "sloppy" higher up compared with a smaller sub doesn't really have factual support.
This isn't factual support. But, many people around here have mentioned how when they run their m80's or m60's as large speakers with the sub off that the bass just seems quicker, tighter and more well defined. Many of those guys have Axiom subs. Granted, running no sub will not have as much low end extension as running a sub.
There are even some reviewers that always run their systems sub-less and mention the reason that they do this is for more musical well defined bass.
I'm more of a movie guy, in my home theater system. So I'm not going to run sub-less, even with a good set of tower speakers. I know that there is plenty of mis-information floating around, just look at the audiophile esoteric crowd on nearly anything audio related. I'm just trying to understand what is going on here.