When and what was your last significant equipment upgrade?

I will start- December 2015, a DAC (Bricasti M1)

As I've said in the past, I truly believe I am done in terms of buying gear, but more recently I finally merged my laptop with my DAC to explore hi-rez audio, which I am enjoying a great deal
I just completed a reference DHT  Triode preamplifier ,
and a F6 Pass labs 1st watt amplifier  this builder is excellent with several degrees in electrical engineering
my pre has the 26, and 101 D  tubes.

A used Matrix M Stage HPA-1 headphone amp/preamp (2012/v.2). It cost little & really impressed me sonically, bettering my Burson Soloist in certain ways. I'm upgrading it with w/OPA627AP opamps & using as my day-to-day preamp.