The commented kit is not being sold currently at dx, but it’s sold at Hobby King ]
There are also others kits like:
It’s really cheap, all the components work flawlessly and very well but IT DOES NOT INCLUDE ANY DOCUMENTATION and some parts (pan tilt base) are impossible to ensemble (it needs another micro servo, 3€/4$) and there is no way to mount on the robot base. Even that, I Think is a good deal, but you should work to get all the needed information (yes, all needed information is over Internet) and put your imagination to build it. I have used Lego Technics parts to mount the ultrasonic sensor.