You are correct on all of your maths but I would probably do it the same way as thenic123 for future upgrades. My build was based on the argon, before the ioni was about. Now, the only thing in my system that I could think to upgrade would be the motor. If I want to do that, depending on the motor I might be forced to drop the Argon and go with an ioni. So if I was to do it again I would go with the ioni HC so I know I wont have to replace that if $$ and motors think I need something more than the mige. It sounds like sine encoders could be a possibility for us in the future, that and a kollemorgan could make me think of going that way and the HC would be ready.