What is your budget?
I just want to point out that the W line of speakers are more on-wall speakers rather than in-wall speakers. I've heard of some members considering to put the W line of speakers into the wall, making them completely flush with the wall, which they are not meant to do. They are an in-wall/on-wall hybrid.
Anyways, for the speakers. Since you have the W3 speaker as the center, I would also recommend using the W3's in place of the W2's as you have selected. Having all the same speakers up front will make them blend much better.
From what I understand, you are sitting 12 feet away from your TV, with lots of room to your left and right. Your selection of speakers will do just fine in that regard.
On placement of the QS4's, you should put them on the back wall. They really should not be "above" you but rather off to the sides. Since you are sitting pretty close to your TV, I would put the QS4's 8-12 feet apart on the back wall at about 5-6 feet high. That would be the optimal setup for the QS4's.
As for the EP175 subwoofer, I would recommend going with either an HSU or an SVS brand of subwoofer. They are much more "bang" for your buck. The EP175 is $550.
The
HSU STF-2 is a subwoofer that is $400 and performs just as well if not better than the EP175. If you look at their VTF-2 subwoofer, it has gotten many shining reviews. The STF-2 performs the exact same way as the VTF-2 does, except it loses its ability to tune to different frequencies, which is a feature most people will not use.
Good luck on your home theater!
