was this project ever finished. I liked the floating design, but one think to keep in mind is to watch the amount of weight you're mounting on to what looks like two studs.
It appears you have about 100 lbs of weight from the flatscreen, and then the speaker is another 5 lbs, but then, toward the bottom, those components with cables hanging off are going to be another 50 lbs or so.
Without having something to help shoulder the weight, it might eventually cause those two studs to bow at the bottom, dangerous!
Usually, when mounting to a stud, there's a bit of weight distributed along the stud, you're distributing the weight from one stud to another, but the weight of the middle between the two will continually be a stress point for the studs, and that is where you might be cautious.
Adding a small 'stinger' support that is flat and triangular can be mounted in the angle between the two walls right in the corner. If colored with the walls it will be invisible, but also give you another axis on whitch to mount and support some of the weight, and still retain that invisible floating look.