Tom, 18 feet is a width I've never tried. I've gone 13 feet with all the Axioms you see in my signature (except on-walls), with great results. The LFR1100A manual suggests 6 to 12 feet. Talk with Axiom about that.

As for amps, you may also want to look at Bryston. You'll need ten 28B cubed per LFR1100A.

https://bryston.com/amplifiers/28b3/

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated