I use the CCA C12s while playing bass and it sounds great! You should try them.
IMO the CCA's and KZ's are basically the same thing, described in reviews as being "sister brands" so I'm assuming they're probably from the same factory etc, similar to Chevrolet/GM i.e. in being "similar". I went from KZ-C10's (which are now my backups) to CCA-C12's which I think are somewhat "better". Both have a V-shaped response curve but with properly sealed tips they're really clear in both highs and lows with sufficient (for me) mids and the bass is definitely solid and punchy. But as others have stated getting a good seal is critical to the overall sound quality and especially to the bass response.
For reference, at the suggestion of my BL who uses Moondrop S8's ($700) I tried a set of Moondrop Blessing 2's which cost 6X+ more than the CCA's ($319 vs $40 - 50 bucks). The Moondrop has a very flat response curve which for me didn't give me near enough high end for my long time rock band damaged hearing. As a flat, balanced reference IEM the Moondrop's would likely be great for someone who wants that flat response. Sold them to a band mate who loves them, but for me the CCA's were clearly better FOR MY NEEDS.
