Actually, you will probably notice how well PK1 can be driven from an iPod unamped. You won't get that great of a bass impact or the best treble extension, but the performance will still beat most earbuds out there.
Obviously E1 will not give you the same performance as a full size portable amp, but IMO you are not missing out much. I compared my PK1 between 3MOVE and E1 and E1 actually holds up pretty well. Not quite as resolving nor have the full bass impact as 3MOVE, but E1 is still noticeably better than my Nano4 headphone-out.