Earlogic, a couple of things here. First, you are playing an acoustic. It's not like an electric, which really loses it's sound if not plugged in. As such, an acoustic will do what an acoustic does well---project sound, even when ampped. In fact, with the headphones on, you are disconnected from the ambient reality, and could accidentally play louder without knowing it. Plus, amps can be costly,and pickups vary all over the place. I would make sure the room i'm playing in absorbs as much sound as possible. Carpet instead of tile, and a lot of sound absorbing stuff in the room. You could make sound absorbing panels to hang on the wall to cut down on reverb. If you have a neighbor on one side, play in a room as far from the dividing wall as possible. If neighbors are on both sides, play in an inner room if possible. Consider a sound hole mute that blocks the sound hole. It is just a plastic insert that totally covers the sound hole. It will likely cut your sound projection 2/3 or more. Also, a softer pick will not attack the strings as hard, which will help. I actually like a soft pick because i can control my strumming dynamics easier. Also, consider loosely tying a sock around the neck of the guitar near the nut. The only thing i don't like about this is you want to train your ears for the chord pitches, and still be able to hear your fretted notes. Also, consider strumming with your thumb instead of a pick. But this method robs you of learning pick control while strumming. I think a sound hole mute is what you need, and you should be able to get one at any local guitar shop cheaply. In the end, i'm with the fretmentor---i don't think an acoustic guitar is a problem, and you can control the dynamic of it by how hard you strum it.