Another note I would also like to say about your experiences is that although the EX600s are higher quality, you may prefer the sound signature of the earbuds (cause they sound better to your ears). This is normal as a lot of people don't like the really quality analytic stuff... Also, your music you were listening to (classical) does require more midrange which is something your earbuds do really well (cause they are earbuds, they will show more midrange over bass, and at times treble). Classical music does sound better with better midrange and since the EX600s have more bass (but generally more balanced), they will be perceived as worse for classical (which isn't wrong, but not right).
My suggestion, try something like an Etymotic for classical to hear a bigger increase (maybe something like the HF5's mid-range focus will be more suiting for you). Another suggestion is to test out tips for the EX600s (that came with it) to ensure you have a good seal if you haven't already.
*Note, I do agree that audio quality and seal do make a difference.