I have owned the Logitech Z-2300 2.1 speaker set for more than a year now, and it has been nothing but great.
The set has 200 watts RMS or continuous power. They are really powerful and can get very loud without much distortion at higher levels. The sub is 8 inches and quite big actually. My only complaint is it takes up a good deal of space under my desk. The subwoofer weighs probably around thirty pounds and is about 15 inches deep.
The satellites have a very nice look to them and sit well where ever you decide to place them. Some people have said there is no mid-range, but I do not think so.
The controller is also nice, although I wish it was wireless. It has bass, on/off, and volume control, with a headphone input on it as well.
Overall, the speakers sound very good, and they can get really powerful. If you're looking for a set for about $100, this is what you want.