You left the Lightspeed Zulu 2 off your list!
I tried all of them at Oshkosh (the vendors set up a sound booth so you can actually reasonably test the noise reduction) and in order: (1 is best)
1) S1
2) Zulu 2
3) A20
So the most expensive one ends up on the bottom of my list. Hmmm...
So which one did I end up buying? The $500 Clarity Aloft in-ear headset. No headband giving me more canopy clearance, no big ear cups means no sweat and they are really, really quiet without batteries. Sound sweet with music plugged in too.
That said, if I flew more than a couple of hours a week (like you seem to do, as an understatement) I would probably choose a traditional headset, most likely the S1 or Zulu 2.