I had the same fears before I bought my e3s, but I really had nothing to worry about.
Once you work out the right pieces to fit your ears the sound is amazing. I use mine for listening to everything from rock/metal, electronic and even jazz and blues and they just suit everything perfectly. There's no lack of bass, and I've found myself noticing small things in the background of songs I didn't even know where there before.
I've tried e2s, and they're completely different. On a pair of e2s the music sounds like one noise, whereas with e3s every instrument is clearly defined, but not so much as to cause excessive fatigue and headhaches which can be common with some in-ear phones (like Etymotics).
I used to have a pair of Sennheiser PMX60 neckband phones, and I've tried Grado SR60s (AMAZING sound) but they don't cancel any noises, and if you listen to your music above a whisper everybody can hear you.
In short; take the plunge, you won't regret it. If you're not a complete imbecile, you'll have no problems getting bass from them.