Socata TB aircraft are 24V.
Re Microair, I would check approvals - these used to be for "experimentals" only.
Re Honeywell/Bendix-King, most IFR pilots I know are not fitting their Mode S transponders - the Garmin one is much better because it has push buttons. For Mode S, Honeywell have reverted to the four rotary knobs which I would never go back to, after using a (Honeywell) push-button transponder.