Firstly I'll say straight off the bat I'm not & never have been a fan of headphones. I don't like using them but in saying that I've only ever really used the Koss UR-30's.
Recently I've decided to give headphones another go especially in windy or otherwise noisey conditions so wanted to get a good set. I did a fair bit of research & found that people were using &/or recommended a variety of different types from 32ohm to 150ohm.
Some of the more popular ones were of course the "detecting" phones like Nugget Buster, Grey Ghost, Black Widow etc. One comment I did find with these detecting type phones was they are built rugged with detecting in mind but may not necessarily be the best sound quality. These are generally 150ohm headphones. Having never used them I can't personally comment but at over $200 this was a comment or factor I considered. Heatho on this forum is also using the Gog headphones from Nenad & seemed to be impressed with them on a recent local trip & quick catch up. I'm sure he'll add more here about how he finds the sound etc. but as he comes from a professional sound background him being impressed with them is a good recommendation for them. I very nearly went with the Gog headphones but being a tight ass went for some other recommended ones that were cheaper as per below.
A "sound" specific brand that I found has a bit of a following in various detecting circles was Sennheiser. I found some gold detectorists in Australia were using the 50 ohm HD558 & HD598's & were very happy with them. I also caught up with Syndyne from the forum recently & he was using the Sennheiser HD-280's @ 64 ohm with success. They sounded pretty good to me & are well built/rugged enough for detecting + very comfortable being designed for studio use. They are also designed for quality sound & good noise attenuation for high noise environments. They have a long curly lead too.
http://en-au.sennheiser.com/hd-280-pro
After some more research & finding that the HD-280's had some good reviews from other detectorists also I ended up deciding to go with them. I got mine delivered for $139.
I think headphones are one of those things that you can get a lot of different opinions & nobody's right or wrong. Even the Koss UR-30's have people that find them quite alright but I didn't. I'm hoping the HD-280's pan out ok?
As you say your hearings not the best trying a few different types may be best if possible. You may need to match the headphones to your hearing rather than what others find works best for them detecting?