the Dtxtreme III is the previous version of the 900 series - Yamaha's top of the line. The module is upgradable to a 950 by a flash upgrade. It is rubber 3 zone pads so each tom pad has the the central head area as a sound, and then 2 more on the rim. The brain is also very expandable for inputs. It's the best brain yamaha makes and a big step up from those below including the 700's.
Used they seem to go for around 2000-2500. It's an excellent e-drum kit. I have a Dtxtreme II which was the previous top of the line yamaha, but it's a step down in features and sounds. I love mine though. They tend to go for around 1200 around here.
Both kits feature hi hats, 2 crashes, ride, 4 toms, snare and kick.
The biggest question with buying e-kits is the drum surface material. A lot of people like the roland mesh heads. Some like the new yamaha silicone heads. I don't mind the rubber heads on the yamaha kits. Alesis kits have a different head as well. Only you can decide for yourself which you like best. You have to try them all. If you are going to shop in the 2000-3000 range for a good kit, then look at the 2-box kit as well. It's a real up and comer.
Digital Drummer is a free mag for all things e-drums. You would do well to go back and read every issue.
I hope this helps.