After reading various surveys and listening to several suggestions I eventually decided to build my DAC rather than buying a new one.
There are various options and components available to build your high quality DAC. I used the boards produced by JLSounds.
Specifically, the basic component I used are:
The nice property of the I2SoverUSB board is that it allows giving power independently to the USB section and the I2S section. The two parts are separated by a galvanic insulation, so that noise entering from the USB does not affect the DAC. A re-clocker is also used on the I2S section to significantly reduce jitter.
The AK4493 board also uses galvainic insulation, to separate the DAC section from signals (e.g. sampling rates, type of stream, etc. ) coming from the USB part and those sent to the LCD.
In order to fully expoit the galvanic insulation properties of these components, I used two separate power supply boards to separately give power to the USB section and the reclocker/DAC sections.
I also used an OLED control board, to be able to setup and check the status of the DAC.
The power supply boards are powered by a toroidal transformer 50VA, 230V AC, to 2 x 12V AC.
To put all togheter I used an 1455T2201 Hammond extruded enclosure.
Here are some pictures of the building phases, and the final version of the DAC: