I bought this in May but have hardly used it, around 20 hours max.  During this time, my dac's usb input (NAD m51) wasn't synching up with the summus so I had to wait until I could get my hands on another dac.  I tried it with a Topping and a Matrix Audio and the summus works fine.  So the unit is basically new.  I'm asking for $2000, shipping (usa only) and paypal fees included.  Note:  The summus needs to be hooked up via ethernet cable to a LAN, no wi-fi.  This is my first time selling on Audiophile Style, but I have bought and sold on Audiogon (user name nealsons) and Ebay (nihackenbush) and you can read my feedback there.