Dig, Welcome!
You've come to the wrong forum as every time someone comes with a plan, a budget and WAF expectations, either we go out of the budget, or (if you're strong) you're able to convince the wife and change your plan, or if the wife wins, you KNOW that you'll have a system that will have some compromises
Considering that you do mostly movies, I would suggest you considering the EP500 (I know, it's easy to suggest when it's not your money
) or at least the EP350. The M80s have very good bass on their own, the EP175 doesn't really go lower and would not really bring anything extra.
I don't think putting the sub inside an enclosure is a good idea neither, you're better off to have a sub try to fit the decor as best as you can but outside.
With a room like yours, I would go 7.1 with M2s for the rears. The M2s are pretty low profile and I don't really understand why you want to put them on their side but it's not a good idea. If you really can't place them vertically, then go with 6.1 with the VP100 in the back. You would probably get some benefit from going with the VP150 as 17ft from the back wall to the couch is a pretty big distance and I would think the VP150 would play louder, filling the space better (note that I have never heard the VP100 and I might be wrong)
