These two earphones couldn't be further from each other. The CKM500 is very syrup sounding with muddy bass. The RE-400 has way more clarity and transparency. Also, the RE-400 has a fuller more 3-D like sound. The CKM500, however, will beat the RE-400 in bass if that's what you in. Simply put, these two IEMs aren't on the same level at all.