my den is 14x19, with the LCD on teh 14' wall. i put it so that the bottom of the tv is roughly 5.5' off the floor and it works for us. we can view it from any angle in the room just fine, but that varies by model so you may wish to look at one that is powered on in the store to make sure.

the way we settled on our height was to put the TV on top of the old entertainment center and raise it up until it was uncomfortable to view from our recliners. since ours had a stand on it this was easy to do. then we move the old EC and stood the TV on some crates to bring it down until we found the height we wanted. i simply measured the height and then installed the wall mount. if you have a couple folks tha tcan help you, they can raise and lower it to see where you want it without having to sit it on something.

crutchfield.com website has a detailed set of guidelines on tv size and location. We have bought several tvs from them and found their representatives very well informed and helpful on the phone. In terms of buying from them, they are not the cheapest, but they more than make up for that with the level of service they provide.