JVN has an excel(lent) speed modeler in this white paper.
http://www.chiefdelphi.com/media/papers/1676
With it you can change the motor inputs, gearing, weight, etc. and it will generate displacement, velocity, acceleration, and current plots.
He removed it from his recent update, so you'll have to go old school and get the old one.
Ken Patton has a similar spreadsheet, but I don't have a location to direct people to.