+1
MacIntosh is probably stating the specs within the audible audio spectrum, which is 20hz to 20khz. It undoubtedly produces output well below this when fed appropriate material. Your bottleneck will likely be your subwoofers not the Mac.
It is unlikely you will notice a difference between the Mac and those other units in the bass.
The Mac comes from decades of producing very high end products. I would put much more faith in the sonic qualities of the Mac over the other brands. Specs have very little to do with what processors sound like. I would read reviews from professional high end home theaters if you want to know what they sound like.
If you are unhappy with the low bass... there are volume controls on the subwoofers you can over woof them.
My system is a Marantz AV10 processor, Parasound 52+ amp and two SVS PB 3000 subwoofers.

