well.. spec's of motors and ballscrews are no secret, but be aware of the fact that every machine has its own ideal setup, my machine is fairly small, i didn't need a big one for the work i've got planned for it.
Yet, the steppers are as heavy as they get in Nema 23 dimensions, i running on 15 mm Ballrails from Bosch-Rexroth, and 12 mm x 2 mm pitch ballscrews, zero backlash (pretensioned version),
this stuff will cost you a lot of dough, , but it will give a proper engineered machine the right accuracy and stability.
Bottomline is: what kind of precision do you want?, let's say you want 0.1 mm, then, aim at 0.05 mm, and choose steppers, drivers and leadscrew to match..
for example, a few weeks ago i made some clamps, all machined on this machine.
the machine is fitted with 8times microstep drivers on 200 steps motors, resulting in 1600 steps/rev, at 2 mm pitch this gives me 0.00125 mm steps, 8 times smaller then 0.1 mm.
after machining 8 parts, i measured some of them, none of them was more than 0.05mm off, and all parts were milled in one pass, no finishmilling was applied..
in the near future: more power, from 18 to 36 Volts, 2000 steps/rev ( 0.001mm true resolution ), and USBCNC control instead of ZEUScnc, rapid 2200mm/min instead of 1000,