The BCTU2A processor works only with the 670 cabinets. It does not work with the DK424 cabinets. If you have the opportunity to upgrade the DK424 to a 670, then you should do it especially if you want to use the BWDKU which the DK does not see as a 16 port card. It is unnecessary to have the PRI card in a cabinet all by itself. I would put the PRI card in slot 7 of the main cabinet. I don't know how many cards or how many phones you will migrate over, but make sure you don't exceed the power factors of the cabinets. Also note that not all the cards that work in a DK can be used in a 670. Eg. PEKU, PIOU, etc.