What is the correct cabinet height for a 50" TV?

My existing cabinet is 33.5" high and I am hoping to place a 50" DLP TV on top of it. The TV I am considering is 46" wide, 35.5" high and 14.8" deep. How do I determine if this height is okay? If not, what is the correct height for a cabinet that hold a 50" TV. Thanks..
My own personal preference is to have the center of the screen at about the same height of my eyes when seated for viewing. So, seating height is a factor, as is your posture when viewing. This is at a seating distance of 10 feet. If you are farther away, I would think elevation is less a factor. Now that I wear progressive lens in my glasses, I hate having to tip my head up to watch the screen.
Hgeifman- I agree with Photon46. Center of screen should be at (approximately) eye height when seated. Does not hurt to also have tweeters of front L and R channels at the same height though not as important. Best advice, don't get old. These progressive glasses work but they suck (if that makes sense).

one-third the height from the bottom. That what I keep reading on the AVSForums. Your TV is 50 inch diagonal? That's a 16:9 aspect ratio display, right? The display screen should be about 24 inches tall or so, right? 1/3 of 24 is 8 inches. so when seated, your eyes should be one-third the way up from the bottom, or at the 8 inch point there abouts. The other 16 inches should be above your eye point then. That's how I would mount it. :-)

What we need to go from here is:

1. what is your eye-level to the floor when seated? (in inches)
2. how many inches are from the bottom of the TV to the bottom of it's screen?