I'm trading my RE0's for either the Klipsch Image s4 or the Audio Technica ES7
I already have the M6's and the Sennheiser HD485, so which item would be the bigger upgrade?
"Upgrade" implies they're similar and one does what the other attempts to better. That's not the case with the S4 & M6...the M6 is more clean and balanced, while the S4 is more fun with more bass quantity. It really depends what type of sound you're after. I haven't owned the S4s since earlier this year, so I'm just speaking from memory.