Ultimate Ears makes some of the best earphones I've ever heard, with the high end UE line made of custom molded pieces with multiple drivers inside. The UE-11 Pro raises the bar to having 4 in each ear, broken down into dual subs, a mid and tweeter. Audio sensitivity is 110dB at 1mW, which is very efficient. Available in a variety of colors and designs (including monograms) for $1150. I believe that's in a custom metal case. [iLounge]
While these are great phones, they really aren't meant to be hooked up to your iPod alone. They will be underpowered by the iPod's little amp. They might sound great, but a good headphone amp is necessary to get the most out of them. Try the products from headroom for home listening. Professionals had better use a post-mixer headphone amp with a clean power source. Results could be painful otherwise. These are overkill for a 300 dollar mp3 player and are best suited for reference-level listening from a high-quality source. One is likely to hear defects in recording quality with a good source. They may be too analytical for some listeners. Something can be said for less sensitivity in headphones so close to the eardrum. Really accurate earplugs like these can be too much input. Yes, hearing loss is definitely likely with earplugs this good. More like a guarantee.