You seem to be equating "louder" with "better", which is actually pretty natural, but not really helpful. People almost always "prefer" the louder speaker; that's one of the reasons why objective testing is so difficult.
Without a switcher that allows you to level-match the speakers and go between them fairly quickly, it's going to be challenging for you to find your preference.
When you're trying to listen critically between models and/or brands, I don't know that it's helpful to include the surrounds and the center.
Better - I think - would be to stick to 2.0 (or 2.1 in deference to the Energy form factor) and listen to some well-recorded music that you are familiar with and enjoy. I'd use a number of selections for variety and to get a good sample size. Perhaps even do the listening on separate days, but use the same material to test each setup.
Listen to some material at moderate volumes and also at fairly loud volumes.
Likewise, make sure you experiment with the placement of each set of speakers, as that can make a world of difference.
I find my Axioms to be very detailed. If you are used to speakers with some bloat in the midrange or upper bass (which is pretty common), Axioms might sound "thin" at first. Upon longer exposure, I've found that they allow me to hear individual instruments distinctly, which is something I really like.
There are lots of good speakers in the world, and lots of ways to perceive value or contentment. The speakers you have are actually pretty good. You might find that the incremental difference is changing to Axioms isn't "worth it", or you might have am "Ah HA!" moment. As Kruncher said, your ears, your room.
