Upgrade spindle to 400W with the fully loaded option


If I wanted to upgrade from the stock spindle and power supply, would I just un-select them and then add the 400W (30353-04) power supply and the 400W ( 30416-02) spindle?
Would I still need the original power supply to drive the stepper motors?
Would spindle control through Easel still be possible?
Would I need the power supply interface PCB? (seems to be out of stock)