What CNC machine do you currently have? Do you have pictures if home made, or was it a commercial product you bought?

A few more kg on the spindle is not a problem for most DIY machines, and in fact helps with cut quality. Also, unless the stepper motor is very small (maybe off a 3D printer) the leadscrew gives so much mechanical advantage that it will usually lift it up no problem.

Also, what do you want to machine with it ? This will all help with spindle recommendations.