Also can someone give me the shortened version on why Mac has different speaker connections for different ohm speakers? I accustomed to wattage doubling in 4 ohms.Many of the McIntosh solid state amps are unusual in that they employ an autoformer (aka auto-transformer) at their outputs. The rationale is basically that the output stage of the amp will then see essentially the same load when a 2 ohm load is connected to the 2 ohm tap as when a 4 ohm load is connected to the 4 ohm tap as when an 8 ohm load is connected to the 8 ohm tap. And consequently the output stage will not have to supply the increased amount of current that would normally be drawn by a speaker having low impedance.
As you noted, with that approach the maximum power capability of the amp is the same in each of the three cases, as it is in the case of many tube amps which provide multiple taps on their output transformers.
What can be said about that approach? Well, it's a design philosophy. FWIW, I would neither be attracted to nor reject a McIntosh amplifier from consideration based on its use of that approach.
Regards,
-- Al