Much of the sound of a DAC comes down to how carefully you feed it and how you surround it. If you look at Allo's devices, they spend a lot of time (and PCB real estate) making sure that they have very clean power feeds at the device level and isolate each stage to minimise cross-talk of noise/spurious signals/whatever. Look at their Katana product (https://www.allo.com/sparky/katana.html) to see what I mean. You still need a RPi to run that.
An alternative approach is shown by Orchard Audio (https://orchardaudio.com/applepi) or HiFiBerry (https://www.hifiberry.com/products/dacplus/), where simplicity rules. I personally run an Orchard Audio DAC and like it sufficiently well to keep it. I've got a number of HFB DACs from previous experiments, and they sound very good, just not quite as good as the Orchard Audio one.