Concerning the VP160 in-cabinet model.
The VP160 is going to be a tight fit, but I think I can make it work without major renovation. From stud to stud, I have 30 1/4 inches. From backside of drywall to heat duct rising from furnace, I have about 13 inches. would probably need to frame the outside of wall with 2x2's to gain a couple inches clearance from heating duct. I don't think the area around the duct itself produces much heat, but I'd probably add some insulation to seperate the 2 just in case. Here's some pictures. of where it'd have to go. The VP150 is fairly centered, off by about 1 inch.
There is a floor just under this spot, so building a support under the speaker here presents no problem.
I might purchase one of these, but I'll probably wait until the last day before I place an order. (Marking my calander.) Do you think it'll really make that much of a difference with my 2 pairs of M22 mains and EP350? I can always send it back if I don't notice that big of a difference, I guess. Probably never see one at this $460 price again.