Hope I don't cause a domestic dispute '
You figured out the speakers on your own. make a simple frame, stretch speaker cloth over the frame and staple it tight. Get four of those speaker quick-release deals (Rockler), and put your speakers inside. And yup... small 1/4" hole somewhere in the back allows wires to be passed.
The doors (totally optional) would be hinged from the sides of the existing shelf units, and the inside shelf would have to be shortened an inch to allow the doors to close flush under the upper shelf, and above the bottom shelf. Pretty standard cabinetry stuff.
Color... sheesh, I like what you already have, so why not continue with the same values? The JVC would be a focal point, and I know I've seen them in black and silver. I thought you wanted to go the separate stand route and I think the shelf/wall color would be pretty clean looking.
As far as future proofing, I don't know what to tell you. I was looking at the 50 " samy, then the 52" Mits, then the 56" samy, and then I finally pulled the trigger on the 62" Mits. If you can afford it, get the biggest set you think you'd ever want. It looks like you have room for a 56-62 inch set (about 58" wide). Maybe not.
Have fun with the sketch.