He stated he wanted closed cans.
Oops. Thanks, I didn't read thoroughly enough
😱
In that case, I still have questions 1 and 2, but I can make some general recommendations..
Audio-Technica ATH-A500 - $100
Circumaural, enormous. Bassy, mids a bit recessed, but reasonably well-balanced. If you don't mind the size, a good all-around choice.
Audio-Technica ATH-A700 - $150
Circumaural, enormous. The A500, but somewhat better across the board.
Audio-Technica ATH-A900 - $200
Circumaural, enormous. The A700, but slightly better.
Beyerdynamic DT250-250 - $180
Circumaural, barely-- about as portable as supra-aural headphones get. Velour pads. Fairly bassy, high-end is a little recessed.
Etymotic ER-6i - $100
Canalphones. Etymotics are typically less bassy and more treble-y than Shures, but the ER-6i's frequency response is adjusted to give it more bass response (presumably because mos iPod's bass roll-off)
Etymotic ER-4P - $200
Canalphones. For all intents and purposes, a better ER-6i.
Sennheiser HD25-1 - $200
Supra-aural. Probably not the best option unless you're after durability and portability above all else.
Shure E2/c - $80
Canalphones. Bassy, seriously recessed top-end. Great isolation at a low price, though. If you own the PortaPro and PX100, you'll probably think these suck in comparison.
Shure E3/c - $170
Canalphones. Bassy, recessed top-end. Very difficult to recommend these when the E4/c's so near, but the E4 does pair very poorly with the iPod (low impedance, and not a very bassy canalphone to begin with-- sounds tinny with it, imho)
Long list, right? And it's probably not complete. Try everything you can before you buy. It's probably not possible (and disgusting if it is) with canalphones, but if you try out a lot of full-size headphones you should be able to get an idea of what sound signatures you like and don't like.