My in-laws have a similar room layout to yours. Where your bar area is they have a built in entertainment center. The TV is on a stand that pulls out and swivels if they want to make it accessible to many viewers. There aren't doors in front of the TV to close it off while not in use, but there are glass front doors where the components are. They aren't big TV watchers, so this works for them. My son has a huge projection TV screen mounted to the ceiling in front of his fireplace and they just lower the screen (remote control) when they want to watch TV, but have it up most of the day. You don't even notice it up there on the ceiling and they can still use the fireplace with the screen down as it doesn't come down enough to block the fireplace. For this set up, you would have to have suitable spots for the projector and sound components. That's a super sweet set up, esp. if you're into movies. We love watching movies at his place. Also, you need to have blackout shades on the windows if you watch TV in the day. I like the concept of a small sitting area in the vicinity of the fireplace and another one facing the opposite wall-if you decide to put your TV opposite the fireplace. Wherever you place your system, it might be useful to have easy to move furniture, so if you have a big group conversing, playing games, watching TV, you can easily pick up and move your furniture to accommodate everyone. Very pretty room.

Like errant said, use an articulating mount placed in the recess. The TV will then be flush with the wall. The ariculating mount will allow you to pull out the TV a bit further out for better viewing, and depending on the mount, you might also be able to swivel and tilt the TV, for even more viewing options. You could then make some panels with black speaker cloth and mount them above and below the TV to make one whole TV/audio wall. Hinge the panels on one side and you can hide stuff in the recessed shelves, behind the speaker cloth, and still be able to access them.

I'll second the articulating mount for above the fireplace. It's your best solution IMO. Pull it down to watch TV and push it back up when you're done. I have my tv over my fireplace and I've found it very comfortable to watch. But we have it mounted low and angled downward, and our seating area is ~14 feet back so the angle isn't at all uncomfortable. Without seeing a pic of your actual space with measurements (how deep is that living room?) it's hard to know if your seating area will be far enough back to be comfortable without an articulating mount - but I can promise you such a mount eliminates any potential problems.

I'm surprised you haven't gotten more comments. I'm assuming your front entrance is there. It would work great to have a couch or sectional floating facing the tv. Get a sofa table for behind it so you are looking at the back and give you a drop off space from the entry. leave a nice wide walkway open from the front door past the stairs to the kitchen. This defines the living space and keeps people from walking through the tv viewing, conversation space. A couch and a couple chairs give more options for furniture placement than a sectional.