The Numa makes use of the KeyB Duo and KeyB Solo sound engine - its kind of a cut down version of the KeyB in many ways.

I havn't heard the leslie on the Numa, but if its the same as the KeyB...it is just staggering! It is the only true Three Dimensional simulator. When you listen through headphones on any other clone (including Hammond) the simulator sweeps across the stereo pan and makes your eyes roll.

The KeyB sim is a full 3D image and the open end of the horn moves toward you across the pan and the away from you. If you use the Leslie brake the horns stop at whatever position they are in at the time. As well as the top horn the bass rotor is also moving and you can also hear sound reflexion.

I used to maintain that a real Leslie was required for a genuine Hammond sound...not any more. As I say I am not 100% sure the Numa has this sim, but if it does you will be stunned.