What would people recommend as a minimum for milling out 1/2" thick aluminium parts? Stepper power, leadscrew size/pitch, and router power?

I'm looking at getting some 1/2-10 leadscrews and I can get between 127oz/inch and 500 oz/inch motors. Several of the routers that people have recommended are available locally as well. I just don't want to get 500oz/inch motors with a 1/2-10 leadscrew only to discover that the motors are too powerful and the leadscrew too wimpy!

P.S. the leadscrews are ACME with delrin nuts, though I do also have a 20mm ballscrew with 5mm pitch (slightly over 0.001" movement per full step w/1.8deg motors)