without question ...Yes E4c will be a big improvement. The thing that makes these amazing is the clarity and sound replication. Amazing. It isn't that "wall of sound" that you find in most speakers. Their great. In some songs featuring a piano, i can hear their feet hit the pedals, and i can here the drummers tapping before the song starts. They pick up everything. You really need to hear it for yourself, but they are great. You can pick up things you have never heard before, and it makes it incredible.
What i can say that the E4c can be described using three words: balance, separation, and fun.
Treble: the highs on the E4c redefine "crystal clear". I no longer need to boost the treble to hear the notes that the E2c struggled so much to convey. I began my listening session with the medium clear sleeves but soon turned to the tri-flanges to achieve even better isolation, and that's when the E4c truly started to shine. The simple fact that the tri-flange actually improved the sound instead of muddying it as it usually happens with other canalphones is a statement to the quality of the E4c. The highs are clear, vibrant, magnificently reproduced. You can at last hear the cymbals in all their glory, something the E2c will never let you do. And most important, the E4c will not sound shrill. The highs can get a bit TOO high at times, but that depends on the recording and not on the phones - actually, it happened only once, and with a 128Kb/s MP3. With all the other tracks, the E4c never sounded piercing or fatiguing, showing the highs but never letting them go too high for my hearing.
Midrange: E2c users know all too well that this phone has a very prominent midrange, which makes highs very hard to hear clearly, and ultimately makes the phones fatiguing after a long listening session. With the E4c, this doesn't happen anymore: the midrange is clearly reproduced, but it is even with the other frequencies, so that you can hear beautiful vocals without sacrificing the instruments. Vocals are detailed and it really seems that the singer is singing right in front of you at times. I could actually make out some lyrics I could never understand before with other phones.
Bass: the bass on the E4c is very, very, very nice. Although it is not as boomy as only a dual-driver canalphone can make it, it is quite surprising nonetheless. The bass is incredibly detailed - you can make out all the different notes with ease, since they're not recessed at all, and they do produce quite some impact on your eardrum, making the overall experience a true pleasure (I did find myself grinning in the dark at one point). The bass on the E4c doesn't overwhelm, but rather complement the other frequencies. The E4c deliver just the right amount of bass for me, and that's why I will go ahead and say that the E4c is probably the first single-driver canalphone that can be actually described as "fun".
The best thing about the E4c, however, is probably its balance. All the frequencies are wonderfully represented, and none of them is prominent upon the others. Also, the separation is phenomenal. You can make out every instrument with ease, and concentrate on the aspect of music you prefer. You like bass? You will hear every note of it. You like cymbals? They will send shivers down your spine. You like vocals? You will hear them in better detail than ever. And your music will have a hard time fatiguing your ears, because you will not need to raise the volume too high to hear any recessed notes - there is none.
So, the E4c are a definite improvement upon the E2c: the comparison is almost unfair. Everyone who says that the E4c are only a marginal improvement is either a liar, or has had his ears spoiled by some custom-molded Ultimate Ears canalphone. The differences between the E2c and the E4c are there for anyone to hear - you'll just have to listen.
E4 has super bass, bit not the boomy "hit you in the head" kind that you find for bass driven tracks. i always keep the bass boost on my SM3 when using the E4c.
sound is amazing and is my reference IEM