C-12 is geared more towards the bass head. Every time I had it in my ears, it took me a while to adjust to the big mid bass bump. In some ways, it felt like a Brainwavz M2++. It basically takes that softer nature of the bass, gives it the extension it lacks and adds more treble and better presentation. The trouble was mids got a little pushed back and had some veil. Whenever my brain adjusted to the bass quantity, I didn't feel the mids were bad or anything. They were enjoyable, but it certainly lacked clarity when compared to my other bass heavy sets like Eterna or E10M or even MH1C. It actually has more bass and better imaging than E10M, but E10M had more clarity, better treble sparkle and a wider sound stage. I felt MH1C's mids lacked a slight bit of clarity coming from other (pricey) IEMs, but it's bass was loaded towards sub-bass, so it has much better clarity than C-12. Except for the cable, MH1C was more in line with my sound preferences.
E30 is more balanced than the others mentioned here.