I had the same problem. I went out and bought some Westone UM2 after that. Wow the bass was better, just as comfortable, and nice for all different genres.
That said, I love my E4c, and wont be giving them up anytime soon becuase they have gobs of detail, larger soundstage, better dynamics (esp. when amped) and work allot better with non bass driven genres of music. Some Dreamtheater, Fleetwood mac, Liquid tension experiment, Mozart, etc. are great on the E4c (i know you have e3c, but they are similar)
The UM2 kill with Tupac, Cypress hill, Ministry of Sound mixes, Bass Mechanic, etc.
So what I am geting to is this: the E3c may work wonders with your genres that it was designed to work with (more "natural" recordings that are more vocal/treble driven). You may want to give them some time and use them carefully for at least a month (that is how oing it takes me to evaluate gear). If you don't like them, sell them here.
Finally, what equipment are you using? You have the Nano. What quality files are you throwing at your 'buds? How loud do you play it? If you want a little more bass and increase dynamics then you can always get a small amp with bass boost (Xin Supermini is excellent) to accomodate the E3c.
If all fails...well....time for other IEM. I definately think that you will like the dual driver IEM like UM2 or Shure E5c. Don't get E4c if you really can't get into your music with the E3c. If budget is issue then get the UE offerings. Shoot me a PM if you want more compare/contrast between the Shure and UM2 or any questions in general.
Oh....welcome to Head-fi. Sorry about your wallet
Neil