@Hooga has already given a great description of the E5000/1000/500 and my thoughts align with him on all three of them. I'd like to fill in the gaps with impressions of E2000/3000, also bonus E4000/E5000 impressions.
Final E2000: The staging is what you notice the most when you listen to them. The vocals are slightly recessed (making them a bit V-shaped) and coupled with the open-back nature and mid-bass quantity you get a quite immersive soundstage. The bass response is mid-bass heavy and lacks sub-bass rumble/impact. Midrange is its special suite as the male and female vocals sound sublime. Has the most amount of treble peaks among all E-series IEMs and can potentially get slightly sibilant on some highly susceptible tracks (Under Pressure by David Bowie, for example). Imaging performance is decent, but not the best in its price class or among other E-series stuff. I'd personally rank them the second lowest among E-series IEMs.
Final E3000: The dark horse of the E-series, and also my second most favorite E-series IEM. Instrument separation esp air between instruments is the best among all E-series IEMs, yes, even the E5000. Bass has more rumble and impact than the E2000 but still rolled-off at the extreme end. Midrange is almost similar sounding to E2000 but has less focus on upper-harmonics resulting in an even smoother midrange rendition. Treble is delightful and portrays all the details without ever imposing itself. If the E2000 is cottage cheese, the E3000 is creamy Gouda cheese. Soundstage is massive, falling behind to only two other <$100 IEMs that I've heard. Imaging is also fantastic in the price-class.
Final E4000: Add more sub-bass extension to the E2000, add a bit more vocal-presence and you get the E4000. A very balanced tuning that doesn't excite anyone right out of the gate but you appreciate it the more you listen to it. I usually recommend it to the mature listener, someone who knows his preference well and wants something no-frill that will be solid with most genres at a budget and won't have the imaging/soundstage/fit issue of the Etymotics. I don't like the stock cable though, I'd recommend getting a third-party one if possible.
Final E5000: Perhaps the only IEM I have ever rated 5 stars on head-fi. They are objectively not the best IEM and many downright label them as
overpriced, but this hits all the right chords with me. I never knew I was a closet bass-head until I listened to them, and the bass on these are world-class, being better than most <$1000 stuff out there barring a certain LegendX, maybe the Hyla CE-5. They are the only IEMs ever that made me fall asleep while listening to Machine Head's The Blackening. The soundstage is cavernous, and while the imaging is hazy the little strums of guitar and intimate pluckings are so well picked out and placed - it gets addictive. The vocals meanwhile make them indispensable for me. I'm a sucker for the HD650 vocals and these are the only IEMs (<$1000 bracket) that get close to said level of precision be it female or male vocals. It's not for everyone, but once you start to appreciate it - it becomes really hard to let go of. The treble has excellent upper-treble extension and while it's not as
on-your-face as on the E4000/E2000, it's the most refined treble in the whole lineup once you focus on the attack/decay pattern of cymbal hits and hi-hats.
Finally, my own ranking of the E-series based on their specialty:
Bass: E5000 >>> E4000 >> E3000 > E2000 > E500 > E1000
Mids: E5000 >> E3000 = E4000 > E2000 > E1000 > E500
Treble: E5000 > E4000 > E3000 > E1000 > E2000 > E500
Soundstage: E5000 >> E3000 > E4000 > E2000 > E500 > E1000
Imaging: E3000 (E500 in binaural tracks) > E5000 > E4000 > E2000 > E1000 > E500 (this one really suffers in non-binaural tracks)
And now, my very biased -
Final ranking: E5000 > E3000 > E4000 > E1000 > E2000 > E500 (a specialty item with limited use-case unfortunately)