I have a pretty robust desktop system. For years I got along with less than audiophile 2.1 speakers/sub. Pretty good, but not as good as possible. Last year I bit the bullet and bought a pair of ATC SCM 12 Pro's. DAMN! Not only are they the best 2-ways I ever heard, but they manage an extreme tightrope-walk of great accuracy w/o sounding edgy/tiresome. Great monitors.
The other big moment was finally getting a non-oversampling (NOS) multibit DAC and replacing my pretty good delta-sigma DAC on the desktop. For the first time in all these years listening to digital, I'm able to totally relax and not hear music files as "digital," just as music. That's kind of priceless...