Hi Steve,Glad to hear you settled on the JBL's. I know you'll be very happy with them. I have both an Eminence and JBL system at home. As good as the Theatre-3's are, the JBL's are way better. Of course, they cost about 5x as much.
Attached are photos of cabinet contruction for my JBL 2235's. Hope you'll find them helpful. Front baffle's doubled up with 3/4" and 5/8" MDF. With a rabbet of 1/2" to flush mount the woofer, you still have 7/8" of material to secure the driver.
regards,
gcl.