This is a very good initiative. It would help if we could add a short description of the headphones. For example, K701 - Detailed phones with wide sound stage.
Good stuff.
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Home: Sony CE595 -> Zhaolu D2.5 -> Mapletree Ear+ HD -> D5000
Portable: Sony DNE20 -> A900
Workout: iPod Shuffle -> Aurvana/KSC75
Good job, it definitely makes it easier for someone who is buying headphones based on their budget.
2 things I would like to mention: Maybe you could sort each category by price. It just follows better as opposed to no ranking for each category. Or maybe rank each headphone by which one is the best but the problem is the second method is more subjective. I would probably just sort them by price.
Second thing. I'm assuming this prices are based on ebay which you mentioned in one of your replies.
I think you should add: "amping is must," "amping is recommended," "amping is unnecessary" because people tend to be misdirected. For example, if I want a detailed headphone with a wide soundstage to use from their iPod, people might chose unwisely.