The motor I use is a maxcim N32 motor and controller,
maxcim motors
The motor is rated for 18 cells but can handle 20 with proper gearing. I ran my revo with it on 14 GP3700's tonight and took first against the nitro's. I was surprised at the top speed I was getting from only 14 Gp3700 cells and a slightly higher gearing. I'm not sure what the run time was but we ran a 15 minute main and I had plenty of power left over.
I am going to get a Lehner motor and bk controller from Mike. I would like to run upwards to 37 volts. I'll probably start out with 22-30v (6s or 8s lipo).