I know the 550 is manually indexed and the 650 mechanically indexed and that the 650 has a charge check station. What other differences are there and how important is the charge check station on the 650? I'm going to get one or the other. I'll reload 10mm, 45acp, 38spec., and 9mm in volumes of about 500 to 1000 rounds/month. Don't mind spending more for the 650. Primary concern is producing safe ammo and based on info obtained here and elsewhere see Dillon as a quality machine.