Since you claim to be buying quality parts, why are you scrounging eBay for junk steppers? Three NAME BRAND stepper motors with the correct 4 wire plugs (and not the 6-wire ones on eBay) and a published spec sheet are $49.95 at TriDPrinting:
http://www.tridprinting.com/Electronics/
They also have a decent price on bulk GT2 belts, sprockets, and several different carbon fiber rod options if you don't have those yet.....
http://www.tridprinting.com/Electronics/
They also have a decent price on bulk GT2 belts, sprockets, and several different carbon fiber rod options if you don't have those yet.....