I am pretty sure that there is a used market for the E5c. Right now there is a lot of excitment about the E4's and the new UE canal phones so you me see more E5's for sale at times. However, people still buy the E5c's (I prefer the E5 to the E4 but my audition of the E4 was at a meet). Whether you should keep the E5c's or get the DT880's is difficult to answer. I had the DT880's in the past and my recollection is they are a completely different headphone from the E5c. You will get a better response if you provide more info such as your planned uses for the headphones, type of music, and source/amp to be used.