Sophie, the Soundstage measurement cannot be trusted under 150Hz. I also think the tweeters of the M5 as measured by Soundstage were not at room temperature. The impedance curve is suspect and that's likely the reason. The tweeters are cooled with ferrofluid and if they were sitting out in a car in the winter, the ferrofluid would become more viscous. This would affect the response.
I trust the Axiom measurements more because Ian calibrates the anechoic chamber to the readings he takes from the 100 foot tower outside the factory. He also makes sure the tweeters are at room temperature.
Note the Aria is not a 3-way like the M5. I expect the M5 will reveal more detail. I also expect the M5 is more dispersive so you will have a wider and deeper soundstage. I expect the Aria to have a "softer" sound which many like but it's almost like having a veil over the speakers.
I have the M5OW in my living room and I've also tried the M5 bookshelf in there. I sit 10 feet away from them in the living room. No joke my nominal listening level is about a half watt. They make great music.
You can read my thoughts at this link. I also have a review of the M5 on the product page. It's the long one.https://www.axiomaudio.com/boards/u...the-new-and-in-with-the-newer#Post439683