What is the best sounding DAC at $2000-$4000?

I did a shootout of my original PWD against the Zodiac gold + Volitkus. It was close to a toss up but I would say the Zodiac probably won by a hair. However, I knew the MKII was in the works at the time, so I held out for the upgrade. The MKII took the PWD to a new level, and to my ears it is now materially better than the Zodiac. Throw in the benefits of the bridge option and the ample supply of very affordable used PWDs and the choise is clear (to me).

Synthesis Matrix Dac (tube) Very musical with nice warm sound. Also has USB port and is in your price range.

Not many people have heard many DACs in the $2-4K range, with the possible exception of a few dealers. There is a thread on Audionervosa that describes a shoutout at a regional meet of DACs in the $3-5K range, including the Perfect Wave (not sure if Mk1 or Mk2), the AMR DP-777, and the Zodiac Gold. Everyone had slightly varying opinions and rankings, but the conclusion was they were all good and fairly similar in sound. You might want to search for that thread. It certainly dissuaded me from thinking about swapping out my Perfect Wave MK2 for something in the same ballpark in terms of retail price.

I would avoid buying any DAC that is not well-known in the audio community unless the manufacturer offers a trial period, because digital equipment depreciates in resale value quite fast, and I suspect you would have a hard time selling a DAC that very few have heard of.

I have become a big fan of the Wyred4Sound DAC1. I have not heard the DAC2, but the USB integration on the 1 is killer and either is in your price range.

Another vote for the PWD MKII. The TAS review is dead on. You really have to reach the $10k summit to beat it. In fact, the reviewer said it occasionally beat his $25k EMM Labs player on some high resolution recordings. Things are changing rapidly in digital right now and I think spending a great deal more than $4000 on digital playback is pretty risky.