Headphones and iems are so different that I can't see how one would make the other redundant. But, if you simply are using the CKN70's the majority of the time and are hardly ever using the S500's (and you don't think that you will), then I can understand you not wanting to keep them. And I can also understand the desire to sell something to fund something new - been there, done that! Fwiw, one reason that I am finally so happy is because with the ath trifecta that I have going on, each item sounds
awesome yet sufficiently different! Each one can handle anything with aplomb, yet I love the AD900X's for rock, pop etc as well as for tv/movies, I love the WS99's for anything bass oriented (ie trance), and I love the CKS1000's for pretty much everything (but, having something jammed into my ears for too long simply starts driving me batty). So I love being able to switch between the three depending on my mood or depending on what I'm listening too. And the trifecta have definitely staunched my upgrade-itis quite a bit (thank goodness)! Sorry for the ramble