On my train commute, the Ipod and Etymotic ER4P serve me well.
Pretty good isolation (I sometimes just have them on without music when I want some quite).
The Ipod can drive them to plenty loud levels even with the ERP4P/S adapter, but it sounds strained. I ordered a fiio amp to see if it makes an improvement (since it is ~10$ and weighs less than the AAA battery, it is almost qualifies as non-amp for most intents and purposes so I slipped it in).