Couple the Shure 3C with the HeadRoom Total Airhead and a decent cable (I recommend the Cardas from iPod to Airhead) and, provided your iPod is loaded with lossless format, you've got about the best sound you'll get for the money. If, on the other hand, your iPod is full of MP3 stuff it doesn't matter what phones you use.

Any noise processing should be avoided, the artifacts kill subtle music.
Go for a proper pair of closed cans, the Sennheiser HD25's
give great isolation, resolve proper bass and are very effecient,you will not need an external amp.
They are comfortable for long periods of time. $250 ish.
Roger