Ed,
Why not just get one of Brian's Dipole Surrounds? Mount it on the back wall, with the drivers firing left and right, along the back wall. Hey, maybe Brian could even wire two inputs, one for each of the dipole driver sets. Plus, you could get the kit, and save money:
DIPOLE SURROUND
Side surround or main speaker with bipolar radiation pattern, dual 6.5” polypropylene or solid graphite cone woofers and dual 1” critically damped softdome tweeters w/control, 16x9.5x8” (HxWxD), 24 lbs. Lite oak, Dark oak, satin black finishes Power Handling 150W. Impedance 8 Ohms, 24 lbs.
KIT w/cabinet $289ea
KIT w/o cabinet $149ea
Assembled $349ea
OPTION: dual Focal inverted metal oxide dome tweeters add $130 per speaker, dual 6.5" solid graphite woofers $120 per speaker
Stewart