Definitely give Axiom a call. I don't know what the deal is with trade-ins. 2x EP350 will definitely make a difference in terms of filling the room, but I imagine an EP600 would roughly match the SPLs and go way deeper than the 350s.

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