Modern DAC Replacement for a Sonic Frontiers SFD-1mkii

Hello all,

I've got a Sonic Frontiers SFD-1mkii that, after some troubleshooting, appears to have the Ultra Analog hybrid DAC going bad in it. I have a couple paths I can take from here, but I wanted to see what you all thought. 

1) Repair the Sonic Frontiers
The Ultra Analog DACs are no longer available. Partsconnexion has them listed, but after a phone call to them they arent in stock. They apparently get these custom made, but with COVID and all the supply issues that come with it, its not looking good that they'll have anything in the near future. Now, there is a retrofit module that uses the PCM63 DAC that drops right in, and with some op-amp changes, I guess it works. I'm not sure I want to drop $300ish into this thing...because aging equipment and hard to find parts. I love the sound of the Sonic Frontiers, and I would hate to give that sound signature up. It oozes fatigueless sound. 

2) Replace it with something modern
Budget is probably in that $1500 range, so that moves me into some decent territory. Pretty sure I can get some demos of units in that price range from local shops. Candidates there would be a Rega DAC-R, Cambridge 851D/N, etc. Really would like something to take in higher res and have a USB input.

3) Replace it with something used, but still modern, in the same price range. Would like to have something that handles USB.

What are your thoughts? Anyone have any experience replacing something of the SFD quality/vintage with something modern. Did a modern DAC in this price category cut it for you?

If it helps, here's a list of my components:
Sources: CAL Audio Delta CD Transport or a DIY HTPC (99% HTPC used as source)
Pre-Amp: Audio Research LS2
Amp: Audio Research VS55
Speakers: DIY 2-way using Morel Premium drivers....loosely based on the Solstice design by the great Jeff Bagby. 
Sub: DIY home built sealed servo-sub using a 15" Rythmik amp/driver

Thanks!