Most satisfying system change in 2017?

Legacy Audio Whispers w/ Wavelaunch. Love em.

My PS Audio DirectStream memory player.  Paired with my PS Audio DirectStream DAC, the best digital sound I've experienced.

swapping out a Hafler dh100 pre for a Modwright 9.0 swl 
solid state rectified........this has been a tube revelation for me.
Very happy with it.
Also my wife got me Dragonfly Red for Christmas.
Originally to use through a Dell laptop but had some issues there
so tried on my wife's ipad to very good results.
Listen to youtube music mostly at night especially NPR tiny desk
studio which are often excellent and lets me hear many musicians
I would otherwise probably not find. Dragonfly good enough to
keep me coming back for more.

Upgrading to all High Fidelity Ultimate Reference power cords for my system

PS Audio Directstream DAC and Player, sounded so close to my anolog rig I upgraded that next to a VPI Prime, did not like the 3D arm so got the Technics SL1200G awesome sound and ease of use, then tried 3 different phono stages and settled on the Parasound JC3 Jr has to be one of the best buys in phono stages