I have pretty much the same set up as you. I wish I had some pictures. Here are some comments, many of which have been touched upon. I have ep500, 180, 80's, which are all in cabinent plus a pair of qs-8's and some in cealing speakercraft Aim7-3.
1. Make sure you get the angles right for the from left and right to the main listening areas. You can't toe in the speakers if you build they box spuare. If music listening is big then you really need to focus on this.
2. You can see some of the other posts I've had but I am neutral on the in cabinent EP500. It is fine. I got it b/c of my wife. It has a separate amp so plan for it space wise. I wish I had at least tried stand alone EP500 to see if the sound quality is being affected by being in a mahgonany entertainment unit. I wanted dual subs but for cost reason I went with one. I am actually thinking of adding an external HSU VTF3 v2 i have sitting doing nothing. My room is 17* 14 * 9 but I also have an open side so the entire area is 17*40*9.
Bottom line is I wish I had done the dual subs however the current in-cab ep500 is fine. It is not a dedicated theatre room so I can live with it.
3. The vp180 is fantastic. I recommend installing it so it sits at ear level. This might make your tv a bit higher than you want. Either way I think you will love this speaker - I do.
4. I have a 7.1 but run 5.1 for the most part. My in ceiling sides are slightly forward of the sitting area due to an air conditioning duct. I have the Q8's on the back wall. They are great speakers also. I don't really hear a big difference. So because I have a zone 2 but no zone 2 amp (I have a pioneer elite VSX-94tx) I use the pioneer for zone 2.
I love the receiver you have. I have been thinking of getting one for my master bedroom where I have a vp150/m22 set up. One day perhaps.
1 M80,vp180,qs8,aim7,EP500,Denon4520,Rotel RMB-1095