Just a question, obviously there is no price posted, how much are you actually selling this rig? You mentioned it cost you around 20k, are you looking for a price around that range? 15? 10? It is hard for non-enthusiast buyers to give a good guess and I honestly believe this is a hard sell for people who know these stuff.
If this is all 20k when bought brand new, then I am surprised as to why these parts are selected. Aside from it is your preference, I find it really outdated for an enthusiast build.
But overall, this is a beast of a rig but just really outdated graphics. Goodluck!