It is FAR easier to develop great quantities of bass in a small room, but the problem is that standing waves or "nodes" are far more common. As such, the quality of bass will probably suffer to a very noticeable degree. This is especially true of a room with the dimensions ( completely square ) that Minh mentions.
The very first thing that i would think about would be room treatments. In a room that is this size, nothing you can do to your system can make as much of a difference as some inexpensive but well built DIY room treatments.
As far as speakers go, i would look for something that was relatively small to medium sized and made use of a sealed cabinet. Look for something that places the drivers relatively close together, as you will end up sitting relatively close to them. The further that the drivers are spaced apart, the greater the distance that you have to sit back from them for the drivers to fully integrate into a cohesive presentation.
You might also want to look for a speaker that has a "focused field" radiation pattern. As small as the room is, you are bound to have quite a bit of sidewall reflections coming into play. This is not to mention that you won't be able to pull the speakers out too far from the rear wall. Sean
>