Not being familiar with Mac gear, it appears to be a very hefty amplifier with some design specs that are somewhat uncommon.
First it appears to produce 450w of power no matter the load 8,4, or 2 Ohm. We more commonly see increases (and sometimes decreases) as impedance drops. The other is the three sets of taps which are rated for 8,4, or 2 Ohm. This again a fairly unique element for their amps.
While I doubt the 2 Ohm taps are necessary, maybe some experimentation between 4 and 8 ohms would be worth while test. This model does stay fairly low going from the baser to the mids and then goes up a good but as it moves up.
First it appears to produce 450w of power no matter the load 8,4, or 2 Ohm. We more commonly see increases (and sometimes decreases) as impedance drops. The other is the three sets of taps which are rated for 8,4, or 2 Ohm. This again a fairly unique element for their amps.
While I doubt the 2 Ohm taps are necessary, maybe some experimentation between 4 and 8 ohms would be worth while test. This model does stay fairly low going from the baser to the mids and then goes up a good but as it moves up.