Distinctive features? hmmmm...well, the McIntosh is the only one with blue power meters.
Seriously though, all three are very powerful multi-channel amps capable of adequately driving any speakers you plan on hooking it up to. They would all do a fine job. I know the Parasound is Class A/AB; not sure about the others. I also know Parasound and Anthem have 5 year warranties; not sure about the Mac but I'll bet it does too if not longer. You really can't go wrong with any of them. If I was looking for an amp in this league, I know aesthetics and price would be big factors too in this league. Good luck.
Seriously though, all three are very powerful multi-channel amps capable of adequately driving any speakers you plan on hooking it up to. They would all do a fine job. I know the Parasound is Class A/AB; not sure about the others. I also know Parasound and Anthem have 5 year warranties; not sure about the Mac but I'll bet it does too if not longer. You really can't go wrong with any of them. If I was looking for an amp in this league, I know aesthetics and price would be big factors too in this league. Good luck.