I would say it a bit different - A pair of XVX will not deliver the same low frequency response as a pair of M9s. They are not equivalent in that the XVX requires augmenting its bass with subs, purpose - built or not. That's part of why the M9s are more expensive. A better compare might be the XVX versus the M7. Both can be augmented with subs (as can any speaker in reality, not just for more bass but to manage room modes).
As a data point - My system is flat down to 10 Hz augmented by 4 JLA Fathom subs carefully integrated with the mains. Upon listening, once might think they're baby Moyas ;-)
You obviously have a very well thought out beautiful system. I can see that you appreciate bass as I do. As I mentioned, similarly to the WAMM, the XVX is primarily designed for two stereo Subsonics to reach its full potential. The M9 or M7 are not designed primarily for subs but certainly will work with subs and sound better, especially the M7.
As far as the XVX LF capability see MC review in HIFICRITIC Volume 15 / Number 3 July - Sept 2021. I will quote some measurements:
"There were many standout results but this one caught my eye: at a truly body-shaking 110dB/m at 24 Hz and with inaudible harmonic distortion, the test set showed a superb result of less than 1.5% distortion for both second and third harmonics, and no others of relevance."
"While the output was rolling off a little below 20Hz, it still sang well at 15Hz with less than 2% THD and, with only the 5th harmonic of note, at a still excellent 0.6%, of quite inaudible distortion (1W). Of the many readings taken up to 200Hz, these at 92dB SPL, the average distortion was 0.2% of 2nd and 0.15% of 3rd harmonic, though with a momentary narrow band reversal at 100Hz to 0.1% for 2nd and 1% for 3rd."
The XVX has been the most extensively measured and reviewed statement loudspeaker in the history of the high end. It has never received anything but the highest of respect and praise. I can only add my agreement. It is a very musical loudspeaker. It's difficult to make it sound bad. I don't care much for ultra transparent loudspeakers that aren't musical. The XVX is ultra transparent and wonderfully musical simultaneously. That's why its owners and reviewers like and enjoy it so much. It will be long remembered, long after the Lyra and Orion are forgotten. It will retain its resale value. History will judge the XVX as a once in a lifetime loudspeaker regardless of the negative comments on WBF.