A small monitor that is honest to 40 Hz, extremely fast and revealing and has a very wide sweet spot is the High Emotion Audio P-7. It is under a foot tall and is easy to drive with both tubes and transistors- it has a very flat impedance curve. It needs to be about 1-1.5 feet away from the rear wall for best results. We've been using a variant called the S-7 (which is port loaded rather than passive radiator loaded) in our recording studio as a near-field monitor. So far it is far and away easily the best monitor I've heard.
[ulr]http://www.highemotionaudio.com[/url]
[ulr]http://www.highemotionaudio.com[/url]