I have a 1000sq ft. apt. It's really just one big open room. I feel like 2 is pushing it even in that sized apartment. Any more and I just don't think it would be aesthetically pleasing. The down side too is that the only obvious place for them is next to the windows and a radiator. Its a north facing window, so not a lot of direct sunlight. Plus I keep the shades drawn all day. I'm keeping the fingers crossed that I won't get fading. Thinking about tinting the windows or something. Not sure what I'm going to do about the radiator in the winter....make some kind of heat shield? I dunno.
As far as noise goes, I try not to play after 9 PM to respect the neighbors. I also have thick brick walls though, and I'm on the top floor. The only person to annoy is below me. To appease the SO, I try to limit my playing to when she isn't home or when she isn't doing anything that requires silence (in shower, making dinner, etc.). I don't play if she wants to read or watch tv or something.