Keep investing in peripherals to make expensive an DAC work in my system, or get a new DAC

I recently purchased a DCS Bartok for headphone use and I’ve had some real struggles getting it not to kill my ears with slam, transients and edgy highs. I have a great Shunyata-based power/cable system, a Innuos Zenith as network server connected with Shunyata Sigma Ethernet, and a number of headphone cables for my Meze Empyrean. I just didn’t like the Bartok’s headphone amp, so I’m using an Audeze The King MkII, which sounds a lot better. I also found that the USB input, while generally inferior, is easier on my ears. 

I liked what I heard at the retailer reasonably well, but did not have a chance to audition on my own system. And I can’t return it.

Anyway, for a system where the transducers are right by my ears I’ve had to make a lot of tweaks and it looks like I now have two options:

1. Put my hopes into upgrading my ethernet connection with an EtherRegen and even more spendy ethernet cables to get a smoother sound AND buy another expensive headphone cable with a warmer balance. AND maybe even try a different power cable.

2. Sell the almost new Bartok at a loss and get a smoother USB-centered DAC like a used EMM Labs DA2 and an Innuos Phoenix for using USB. This will ultimately cost me quite a bit over what I’ve already spend (yikes) and take me away from network playback, though my Innuos is a streamer anyway. 

At what point do you conclude that it isn’t the digital sources, cables etc. and just get a different DAC, after having sunk so much money already?