I have Cadet in wall heaters throughout my house including basement. All of mine are 1K watts although I do have a few older 1.5K watt ones in the basement not the 4K like you are thinking about. You can definitely hear them, but like Olyteddy said, the cycling is when you will really notice them, once they are running, you tend to tune them out. How many of those are you thinking about in the theater room? I think one would be plenty and once its up to temp, with you guys in there and the insulated walls, its not going to cycle that much.
I personally love the Cadets as you can set each room's thermostat which is nice in a basement that isn't always in use. Plus they are fairly efficient and here in WA it is cheaper to run the electric Cadets than a gas or propane furnace.
One more thing, someone mentioned air conditioning... I checked out your proposed floor plan and In a theater with an open back in a basement in WA, I don't see how you could possibly need A/C. I'm in Gig Harbor and in the dead of summer with a relative living in our basement full time, it never got over 70. If you had a fully enclosed and double insulated theater, that might be a different story.