I think it's all about the HT aspect of a system. If there are instances when all of the drivers are firing simualtaneously, I'd rather that they were designed as a "set." They were built to function together, tested that way and with a somewhat compromised (reconciliated?) goal to begin with (HT and Music reproduction).
I've sub'ed my old Snells for my M60's. They just don't do as well when used for HT. That thinking is what made me buy the ep500. If I had the space I'd have a nice $6k pr. right next to my 60's with their own monoblocks and pre-amp. That'd also render the sub less important (for music), 'cause $6k speakers shouldn't be asking for that much bottom.
Even some great mfr.'s out there really only take their well-established and well-received towers and throw in a couple of under R & D'd "surrounds" and a "front." Now you're shelling $10k and up for something that was never really designed as a suround system. Great music---HT, ah, not so much.
Researched, shopped online and real time for 6 months. Lucky enough to have 2 audio high-enders within 25 miles.
If you're not committed to spending twice as much or more, the differences are likely to not be significant enough to justify the added costs.
