The RPi board by itself with one of its USB ports driving a USB DAC.
If the DAC does not have a USB input you can add a SPDIF board on top of the RPi and use the SPDIF output to drive a DAC that has a SPDIF input.
And you don't have run Roon. Inmate Cut-Throat runs piCorePlayer and LMS with his Raspberry Pi based streamers. You might see him here and he's often in the Computer Audio asylum.
These are a couple Raspberry Pi based streamers that use the USB output from the Pi to drive my USB DAC. Both RPi are identical except for the case I chose.
Here's the Allo DigiOne SPDIF board that plugs-in on top of the RPi to give you SPDIF output. 
Here's one of my Raspberry Pi's with the Allo DigiOne board on top.
And of course, you can buy the Raspberry Pi, DigiOne board, case, and software ready to boot from Allo. This would be the Allo DigiOne Player that I linked to in my previous post.
