IMHO, the best combo DAC/streamer that is fully RAAT compatible for around 2 grand is the Lumin D2. I believe it’s the best sound you can get for the money. I use mine as a desktop unit, connected to a Schiit Jountheim headphone amp via XLR ports. It can handle up to DSD128 (for which there is a lot of good material for sale).
Now, if you really want to go DSD512, try to hunt for an Oppo Sonica DAC, currently discontinued, but if you can get your hands on one, just do it. I use it with HQPlayer for upsampling, and its sound can be described as “creamy” in DSD512 and PCM 768. Mine runs in my main system fronted by an Odroid C2 on Ethernet with networkaudiod.