With a 1 HP motor, you can stop the motor if you get on it when grinding on the platten. When grinding on the wheel, it is harder to bog down but still possible. I would def go with the 1 1/2 HP. If you could go with 230V, I would. Then you could go with a 2HP... Bill S.'s link has a 2hp 230V TEFC for $120. Only draw back would be the 3650 RPM, but you could get around that with the step pullies that you have.
BTW, I had a Coote and was pretty happy with it.