My problem: I've got a concrete supporting wall where my rear in-wall surrounds should be - I thought it was drywall and my wife was really happy when she thought we were getting in-wall speakers.

Neither of us are happy with the look of rear speakers on mounts. We really want something paintable in our living room. Our setup:
Marantz SR5003
Xbox 360
BluRay HTPC with HDMI audio & video
Definitive Pro 1000 fronts
Definitive Procenter 2000 center
Definitive Prosub 800 sub

Considering both my back wall and ceiling are concrete, and considering the AW5500 is paintable and mounts horizontally, on paper they look like a great solution but I've got no way to test them with similar acoustics.

Think these will sound acceptable wtih my setup?

Thanks, all.