Thanks for all the help! My result now is satisfying, but I still miss the <25hz content. I will be trying an Earthquake Supernova 15" sub (which goes down til 16hz) and see if my room can handle those low frequencies. If it can, I will make a DIY build to handle everything below 30hz and keep my JBLs for >30hz. I will of course compare the DIY sub to the JBLs above 30hz too, but them plan is to have both.
JBL ScreenArray Cinema | 9.4 Surround | 136" Scope