Just to be safe, give Axiom a call -- "I have M3s, I really like them, moved into a bigger room etc...". I'm pretty sure they'll say "50s" but never hurts to get another opinion.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8