@corelli @sbayne I may try a sub in the future. Sounds silly but I just find it hard to justify the use of the a sub when the speakers are so large to start with. It's not the most sane rationale I know...
Speaking of sanity or not, I ran an SVS SB 13 Ultra with my Spatial M3's and thought it integrated very well. As did another owner of Spatial M3's when he was over for a listening night. Open baffle vs boxed sub bass, how dare I. Lol