Front projection takes some thought, and you should NOT get the AE8000 unless you intend to darken the space significantly. It's not as bright as most of the competition, and the BenQ HC2050 is a better value in a non-controlled space.
How long do you plan to live in this home?
Is the space already finished, or are you having it built out?
How much control do you have over the lighting in the basement?
At the end of the day, front projection is amazing. Plan on about 10" to 12" of diagonal for each foot of viewing distance. So, if you are sitting 12' away, a 120" diagonal screen is typical, and 135" or 144" is not 'overly' large for many. People get some idea that you can't achieve what movie theaters deliver in your home, but that's not at all true. The current crop of home theater projectors is often as good, or better than what most movie theaters can deliver.
4K is a joke right now, so don't worry about getting it. On a 55" television, there is basically zero improvement by using it if viewing from 10+ feet away. Save cash, if you need to, or just get it, but it is just a TV. It is nothing like home theater with front projection.
For your basement, an open concept is fine, but you just need to control your lighting. Directional spotlights (3" directional) are great for lighting areas away from the screen. A separate zone of general lighting (or two) around the screen, and an additional zone for the rest of the space is a good starting point. Paint with darker colors around the screen area, including the ceiling. An open concept with some breaks in the spaces works really well to allow you a darker theater 'area' without enclosing it off as a dedicated space.
As I said, it all takes some effort. If you don't really want to put in that effort, then I would go with a flat panel and call it a day. Just like most people do.
For a lighting example look here:
http://www.avintegrated.com/lighting.html