Stepper Motor Drive Capability
Power = Force X Speed in linear mechanics.

In rotatory mechanics:
Power = Torque X Angular Speed.

So, if you reduce the speed, you will increase the torque for the same power (and motor).  If you use a motor with a transmission attached to it, you will reduce the speed but increase the torque.  You can find many NEMA-17 motors with transmission included for about 20 dollars on eBay.  Even, if the torque magnification es enough, you can hold the position of the load without energizing the motor.  And that is the magic of mechatronics, it includes Electrical, Mechanical and Electronics Engineering, plus Computing and Programming :o)