I've got the CM7ti and E3, and prefer the SQ of the CM7ti. I'll be bold and say most people think the E3 sounds better than the E2 (which I haven't heard), but some think the E2 better.
I think the EC7 is supposed to be similar to the CM7ti, and if so, the clips are there for a purpose in that they keep the earbud right against the ear. If the SQ is the same, I would go for the EC7 because that is my only problem with the CM7ti - it doesn't stay put in the ear. If you move around and they dislodge slightly, you lose a bit of SQ. If just sitting there though, I love the CM7ti's.