Help me choose a right TV

[EmeraldCube]

So I want to buy a tv. I will use it as a normal tv(channels and stuff) and I'll hook it up on my PC and I'll use it for watching movies, videos, surfing the web and some non shooting games. I want it to be a 4k and under $800. If it's something a little above $800, it better be good because I'll have to wait another extra mounth. Now I want it to have a great contrast but not only at the middle of the screen but through the entire screen, I don't want the picture to fade. I don't want it to be bigger than 50" because they're much more expensive? I don't want it to have a lot of motion blur because I'm watching a lot of sports. I will be sitting close to the sreen(less than 3 meters).