Peter, sounds like we need to head up to Jupiter Creek and you can try a few sets on my test bed.
At the moment, here's the range of headphones I have laying around:
Recon-ST
Koss TD-80
Technics RP-DH1200
Technics RP-DJ1200
Yoga CD-300
And hopefully soon some SteelPhase cans, when Pat sends me some
Sound wise, the best headphones I have used for metal detectors without an Enhancer are the RP-DH1200's. BUT, they are heavy, the ear pads are not very thick, and they have a tendency to slip off your head. Mine have obviously got a bit of dust in them and have started to "creak". They also are not the best at blocking out wind noise. E.g. they probably fit the needs of a DJ, but are far from perfect to a guy walking around the bush with a metal detector, who is constantly bending over to dig holes.
The thing is when you put a steelphase enhancer in the mix, the 5% improvement on certain headphones is redundant, because the enhancer errr enhances the right range of frequencies that we want to hear, and gives you volume, so suddenly even crappy headphones can sound good. I also think high Ohm is less critical. I have used 16 Ohm earbuds which are average at best when plugged direct into a detector, and suddenly sound very loud and clear when connected to the SteelPhase. So features like comfort, robustness, length of cable, ability to repair if something goes wrong etc. become more important.
I'm using the Recon-ST's with my Zed together with the SteelPhase and am very happy with this combo. I have an old pair of Sunrays for back-up which I've bypassed most of the switches and upgraded the old worn out earpads.