A workstation is definitely overkill for audio applications. If you're only using the PC for audio purposes and not 3D CAD / rendering then save yourself some bucks and get something like a Beelink EQ12 - link.
You can pop the top off and add a SATA SSD to store your music in case the included 500 GB isn't enough. Here's a nice review - link.
There are also measurements showing that it doesn't add any noise and jitter is virtually non-existent when paired with an asynchronous USB DAC like what your Oppo has - link.