My understanding of the recommendation is that:
- 800W spindles are good to go with the Z plus
- 2.2kW are definitely HDZ territory
- 1.5kW sits somewhere in between, so while it should work, the extra weight could induce additional wear on the leadscrew in the long run.
There have been a lot of threads around spindle choices, if you want to keep your Z axis and play it safe, you may be interested in 800W models, it is quite rare to max out spindle power anyway before some other element limits the cutting parameters anyway (deflection, chatter, chip evacuation, etc…)
Any spindle will work with Carbide Motion, as the spindle control uses a signal (“PWM”) that the Shapeoko controller generates natively, and that Carbide Motion supports (through spindle start / stop commands included in the gcode by default, even when one uses a trim router)