You really don't need an in-cabinet VP160, as the regular 160 is front ported so it can be stuffed into a cabinet very easily, but if you want the in-cab versions they will sound identical because the cabinet volumes are the same.
I was working on a system using sketch up that had in cabinet M80s and a VP180 but I can't find it anymore. It was a huge cabinet, similar to what I have only where I have regular M80s, I had made a cabinet for them to fit in as well as the VP160. The whole thing was ~14' long and 3ft high in the center with the outer 'towers' 4 ft high, the TV would have sat in the middle between the towers.
