If you ever looked at Japanese audio magazines, you will see a lot of systems in tiny apartments that seem to defy logic--they are HUGE horn systems. The reason for horns is that they actually sound fantastic at whisper quiet volume levels. Aside from the footprint of the speakers themselves, these types of systems are quite apartment friendly. They also tend to be very efficient, which allows for the use of the best sounding amps: low-powered pushpull or single-ended triode amps.
Another recommendation I have, in addition to those I mentioned earlier, for an apartment speaker is the Gradient Revolution. This speaker can be configured (the bass section can be made to fire in different directions) for a fairly wide array of setup options, including against the back wall. I have heard it sounding really good in a small room and at fairly low volume. One downside is that it is not very efficient.