Are these stepper motor kits good? Or Chinese fly-by-night vendors?

These kits look too good to be true. Anyone had experience with them?

SHIP from USA Warehouse 3Axis Nema34 Stepper Motor Dual SHAFT1600OZ 3 5A CNC Kit | eBay

How's the best way to calculate what size to use on each axis?

On my old Gorton each shaft requires the following to move (no gearbox):

X axis: 64 inch ounces
Y axis: 240 inch ounces
Quill: 160 inch ounces
Knee: 1700 inch ounces

Any suggestions appreciated!

Thanks.

Bob