Here is one thing that I haven't really thought about yet. My only detector is my Ace 250. It only has 3 or 4 different sounds, making it simpler. Perhaps, for now, I might not REALLY need headphones. I am planning on buying another machine in the future, so I'll do some more research on just what headphones I will need.
Of course, if I get the NOX 800, it comes with them...
I had an Ace 350. There are no tone nuances with an Ace, but you will notice a nice increase in battery life using headphones rather than the external speaker.
Those Garrett Easy Stow phones worked well on my Ace.