I spend a lot of time listening to DACs in this price range. There are some great suggestions above. Particularly I hear great things about Merason though I have not heard it personally. Two that I didn't see come up that I think you would find interesting are:
Canor DAC 2.10. It is ESS based but with a tube stage that softens the edges from that chip and list is $4K. I have several dealers around the country where you can here it and I also lend this out. 8 or 9 filters are available and it fully unfolds MQA. Tons of detail, nice staging and not fatiguing.
The Audiobyte HydraVox is an FPGA DAC with tons of detail and a huge soundstage. It has a reputation for being quite natural sounding and is the FPGA side of Rockna. Lisit is $4500.
Having had several oppo products here as points of comparison I think both would be very appealing as an upgrade. Neither is in the league of the Playback MPD6 or MPD 8 but if you listned to either alongside the Playback you would get why I am suggesting them.
Full disclosure, I am obviously a dealer for these products along with Playback designs. If you can, do your best to try and hear the product in home in your system. If does make a bid difference.