When I decided to pick up the UDG U8200 case for my Sennheiser Amperiors, I paid close attention to reviews by owners of the HD25-1 II, since the Amperior is merely a tweaked version. When I saw that three HD25 owners used this case without complaint, I ordered it immediately.
Five things to consider if you're thinking about buying the U8200 and own some version of the HD25:
1. Because it isn't specifically made for portable headphones, the U8200 takes up far more space than a more tailored case. This makes carrying your HD25s less practical in tight circumstances. Bags which fit my Amperiors comfortably now prove a tad too small.
2. The case is a bit roomy for the HD25-1/Amperior, which slides around. This means that any owner of reasonably compact headphones will have to pad the inside of the case.
3. The case does not come with cushioning, foam or even inserts. This is understandable, since it isn't tailor-made for any particular kind of headphones, but it means the user will be tasked with finding a solution.
4. The extra room isn't put to particularly good use. There are no pockets for cables or adapters on the inside or outside of the case. Perhaps the best solution would be to buy a small soft case for cables and then use it anchor the headphones, but -- again -- that solution requires the owner to spend more time and money.
5. It is not a terribly hard case (like those made by Slappa or V-Moda). It seems hard enough to protect headphones in most situations, but the sides do flex.
If anyone had alerted me to these limitations, I wouldn't have spent $40 for a minimal and generic case, and I certainly wouldn't have agreed to pay extra for shipping (it was only available from a third party). I'd either have bought something cheaper or more specific to portability and travel.