That (original link) motor looks nice, but it has a very bad efficiency, at the top end it is less than 50% efficient, that is, it draws 1600W and provides just 700W to it's output shaft.
And on the top "speed" (rpm wise) of things, it is unable to provide any torque at all according to it'S spec sheet.
I'd say a nice engine for a RC application. but as soon as you apply weight and thus need torque it's going to drain your batteries faster than what you have
the my1020 (thesciman's link) I don't need to say anything, that's in almost all electric scooters, most of kids e-quads and so forth.. Nothing fancy, good choice.
If you want to step up, I think you should think about a starter motor.
Say from a 3.0ltr TDI (12V and most likely around 1400-1600Watts), I know that'll require some tinkering with the controller, but it's cheap at ebay and nearly bulletproof.
You also will need to modify the motor itself a bit (diygk homepage provides a howto.)
Or use a truck starter (24V and almost every power from 2kW up to 12kW)
just see what you can find on ebay or CL for example.
In any case, check that you can find a controller for the voltage & amperage you need
before you actually buy anything, it doesn't help to buy a motor for $30 that you need a $900 controller for to run it
'sid
