New DAC or New Speakers?

Speakers are the most subject/personal choice in any system. You should be set on these first and feel they are your long term end game....plus logistically they are bulky & difficult to move. A night and day difference in configuration: horn - line array - 3 way - 4 way - tweeters...a very personal choice what sounds best to you....and even more so on how you listen....analog, digital, stream, HDMI/TV. It takes a lot of time, listening sessions (travel) to hear, and effort to lock in on a speaker choice. You have really good speakers....if you are not set or feel the need to add a Sub…time to upgrade.
DACs more of a narrow niche...at your price point you can get a exceptional DAC and likely a good clock to match. My last & final component I chose to put into my system was the Berkley Audio Alpha 3 DAC. I would also offer that new & better DACs coming out every year. 
Buy your end game speakers...& get a decent quality (used) DAC now...down the road, if you feel the need = upgrade the DAC in 5 years. 
 

Maybe first treat your room if not treated. Even a little goes a long way. Speakers are  most important.

Without question, change the speakers.  Differences between DACs are rarely night and day, but changing your speakers will have you up late into the night rediscovering your music collection.

Agree that speakers are where you want to start with system building.  And going from your Harbeths (86 db efficiency) to the Devores is a pretty significant change, requiring far less power to drive.  What about the Devore appeals to you? Another highly efficient speaker at about $20k that is really impressive is Wolf Von Langa Son.  A speaker that comes from the same sonic direction as Devore is Audio Note An-E.  Have you considered Tannoy or Fyne coaxial designs?  You can get some pretty nice models within your budget.  Last thought: if you like Harbeth sound a lot, ProAc and Spendor seem like natural alternatives to consider.

@mdalton I demo'd quite a few speakers, including Fyne and Proac (they were great speakers) and Spendor 2/3 Classics (that I really did not like) - the Devores were the only ones that wowed me. Hard to say that the wow factor wasn't attributable to the amazing room, the 50K DAC feeding them, etc.... But it was the only room that blew me away. 

I like the idea that they're more sensitive. I've discovered that I am a tube guy for sure. I love my VAC Sigma 170 amp that puts out 85 watts and I plan to use it with the Devores, but I see myself moving to a SET amp in my future.