Most satisfying system change in 2017?

Another was moving from older Garrard 401/ply plinth to a newly refurbished AudioGrail 401 in 3" PA slate plinth. Cleaner and faster.

After 5 speakers including 2 in the $15k  + range
The Pure Audio Project  15 neo  open baffle speakers with the Voxativ drivers 
And very minimal crossover Leonitis . Which gave the the opportunity to max out the crossovers potential since it sits open in the back . The Voxativ full range  driver is very Special and  only used from 350hz on up to the dual 15 inch Neodymium Bass drivers ,and 95db efficient allows you to experimrnt with loads of amplifier options. At just over $8k with the optional Verastarr wire harness .
Very Natural and bettered the other 15k+ speakers I had  totally satisfied Finally.

In all honesty EVERYTHING was a big deal this year.
Lets see
Discovered streaming and Tidal via Bluesound Vault 2...check
Replaced my McIntosh preamp with Exogal Comet Plus DAC/Pre..check
Replaced my old Focal speakers with Wilson Witt series1...check
Replaced all interconnects with Nordost ones, speaker cables with Analysis Plus Oval 9....check
Replaced fuses with SR Black....check
Replaced my Clearaudio tt with one I have lusted over for years, a Nottingham Analogue Spacedeck cw Shelter 501 mk3 cart

Just hard to pick a winner here!
Time to sit back and enjoy the music

Additions...
Multibit upgrade to Schiit Gungnir
Schiit Freya
First Watt F7- now music from the Silverline Prelude Pluses finally sounds wonderful

Upgrading from unshielded Volex power cables to unshielded Signal Cable MagicPower cables on all my sources, phono preamp and main preamp.