I have IE300s and ditched the stock cable for a few reasons, mostly bc it was very microphonic rubbing against my shirt or just amplifying my footsteps into my head, and bc of the fiddly earhooks. I got mine for about $200 so i didnt feel as bad modifying the iem shell to fit a standard mmcx cable, basically i just took a razorblade and sliced off the little plastic rings that make the mmcx connection recessed. im not sure if other people had to do this after modding theirs but I had to superglue the new cable on to keep a secure connection (superglue can be dissolved with acetone or just broken with force so again didnt feel that bad).

if you find a nice cable you like more than the stock one and you arent planning on selling them i would recommend the mod, but then again IE600s are like $700 or something so definitely do some more research before slicey dicey. maybe some boutique seller offers Sennheiser iem compatible cables or something idk