There has not been much mention of the Clearpath/Teknic brushless servo motors on this site, but they are an amazing evolution in motor control. Watch the video on their website, and log into the site and register your name. After you register, you can do comparisons of the many motor combinations they make, and look at the rpm/torque curves for the various voltages and motor sizes.
The motor driver electronics is built into the motor, and can be tailored through a PC program connected to the motor electronics by a USB connection. Once the factors have been qualified in the PC program, while the motor is connected to the machine, the motor goes into a setup mode that sets the software factors automatically, which takes about 5 to 15 minutes.
The company is so confident of their motor design, the have a 90 day period during which you can either return the motor for a 100% cash refund, or do an exchange for a different motor type/torque/rpm factor for your application.
Their engineering is clearly a quantum advance in brushless motor/control design.
John