If you are running a grizzly the best bang for the buck would be to change the pulleys to get the machine up to 3500 RPM (if you have not done that already). If you want to control the speed I believe you will need a new motor and a controller that supports it as you probably already know. The Syil kit might require you to use all Syil electronics, not sure. Anyway, to get more power I did not find an economical solution that would keep the head at a reasonable weight and/or that would fit inside the head. Also the 1.34hp of the original spindle (if that is the one you have) already allow you to take cuts that abuse themachine rigidity. So whike it might be fun to get more hp in the spindle you may have throuble taking advantage of it.