Fiio E10 is pretty good as a starting amp.
Did you volume match the output between amped / non-amped? Common fault with comparisons is having the amped slightly louder than the alternative (straight out of the DAP). Louder sounds better to us - which is where you get a lot of 'night and day' BS about better sound-stage, better quality bass etc.
Most IEMs (not all - but the vast majority) are designed to be run straight out of a DAP. They are generally low impedance, and reasonably sensitive. As long as the damping factor between your DAP and IEM follows the 1:8 rule - you should have no issues - and an amp is not necessary.
What an amp is good for (with IEMs) - IMHO:
- Hardware EQ (eg bass boost)
- Correcting an impedance mismatch (which may produce hissing)
- Colouring the sound (eg Fiio 'warmth') if you like it that way
- Driving the occasional hard to drive IEM that actually requires amping.
What an amp is used for (aside from the above) - again IMO:
- Following the hype train / crowd think
- Making you feel better about being an "audiophile" (I'm not an audiophile BTW - I just love my music)
- Introducing physco-acoustic and imaginary audio bliss (because I'm not supposed to say the pl---bo word)
My personal preference with the IEMs I own (and in particular the SE535 Ltd Ed - which is low impedance and very sensitive) is straight out of the headphone out of my iPhone4 (which matches the 535 impedance requirements nicely). I use apps like Accudio or Equaliser to add decent software equalisation software. End result - great sound - great portability.
As an ex owner of the E7, E11, and IMO exceptional Arrow 4G - none of those amps did anything for any of my IEMs - which is the main reason I no longer own them.
Unfortunately for most newcomers - the only way you can tell is to try yourself. Just be very careful about volume matching. Compare without any EQ. And do it blind (get someone to switch amped vs unamped so you can't see). It's amazing how many preconceptions disappear if you follow this recipe for testing
Interesting - the Classic must have crippled amplification. I owned the 325is - and they didn't need additional amping on either an iPod Touch G4 or iPhone. Another very easy to drive headphone IMO. 32 ohms resistance and extremely sensitive at 98 dB (SPL 1mW)