I wouldn;t recommend 4K. At least not any of it's current incarnations. Many still suffer from typical LED-LCD problems - Poor off axis viewing, uniformity issues, etc. Plus the lack of 4k content and discernible difference is debatable. Don't forget viewing distance is a huge factor as well. If you're sitting 13 feet away and looking at a 60 inch set, you likely won't see a difference between 4K and 1080p. And a 4k set now is not furutre proofing, especially with 4K OLED coming. If you *really* want 4K, wait until Vizio releases their 4K sets for a much more consumer friendly price later this year. If you aren't a fan, at least it should force other makers to lower their MSRP.
Especially in the 1200 dollar range. Your only option is I think like a Seiko 4K t.v that has gotten horrible reviews.
If you can find it, grab a Panasonic ST60 plasma. It's CNETs first ever 5 star reviewed t.v and retails for around 1399-1499 new. Out of your budget by a couple of hundred bucks but still the best bang for the buck.
If you want to go cheaper but don't want to skimp on quality, grab a Vizio E550i-B2 http://www.amazon.co...vizio m551d-a2r
It's been getting a ton of great feedback over at CNET, AVSforum and other a/v sites and it's only 750 bucks. It also goes up to 60 inch for 941$ http://www.amazon.co...ords=vizio 2014
And remember, 120Hz is not true 120Hz on television sets so you won't be getting your PC to display at 120Hz. Yes, it is useful for sporting events and whatnot however. The Vizio sets are 120Hz with backlit LED, 3 HDMI ports with optical audio and has apps like Netflix, Vudu, etc. Oh and built in Wi-Fi but I think that is a given these days.