I owned the m60's for a few years, and my room is huge, around 900 sq. ft., they were up to the challenge with no hint of distresss. The m80's do give you a little more detail and maybe a little more bass extension, but most would not know the difference unless they did a true blind A/B test.
Bob, if you've ever heard B&W's, the Axioms are similar sounding to the 703s' ($$$$$). Or I would say they are also similar to the Paradigm Studio or higher series.
I've owned Klipsch and I like the Axioms better. Can't help you on Energy or Rocket, however Tharkun (old member) had both the 80's and I think the ones above the Rocket 850's and he told me once they were very similar at most volume levels.
