Series of IDEAS about Fireplace TV:
1)The flat screen tv (up to 55 inches, depending upon cabinet dimensions) sits in the cabinet and lifts from the top at the touch of a button. When we want to watch it, the tv is easily accessible. But when we do not want it, it discreetly hides away and most guests do not even know it is in there. Very popular in Europe, they are now becoming available in the US. The one pictured here is from Ethan Allen (Townhouse Video Lift Cabinet), but they can be found elsewhere by googling "Video Lift Cabinet."
2)In rspknse to the question of where to hide components, get an IR repeater which allows you to control the dvr, cable, tv dvd etc without clear line of sight meaning they can be in a closed door cabinent. All the remote need to "see" is the tiny box that all of the components are connected to...so easy to install -- we have them on all our tvs and you wont see a cable box at all!
3)New ultra-thin flatscreens (I'm installing a house full of LED models that are about 1" thick) can look like "art" - provided you can recess the mounting bracket or arm. There are products available to help you do this -- without terribly expensive wall reconfiguration. This one from Sanus is designed to fit between 16" on center studs and accomodates fully articulating arms that support TVs up to 55" or bigger. They are pretty reasonable at about $150-200 +whichever arm you choose + installation. http://www.sanus.com/us/en/products/visionmount/other/LR1A