Sennheiser studio, mixing headphones, trade/buy

Sennheiser HD560s: while excellent as an audiophile listening headphone, these are best known as reference grade studio mixing headphones; highly detailed and revealing. Will sell these outright for $130, about half price of Sweetwater, Crutchfield or other reputable dealers. Sennheiser HD6xx: classic audiophile 600 series headphones. Some think similar to HD650 and some think the best version among the 600 and 650 models. Very hard to find now that they are no longer available from Massdrop. due to my use for a very specific purpose, I will only consider a trade for the HD 600 model in excellent condition (or maybe a Very tempting offer) . Both phones are an excellent condition and feel free to try them out. If you have read this posting, you can assume that they are available. No need to ask.