Do I need a streamer?

I'd suggest what many have said, dump the computer and go with a dedicated streamer.

If not then you could use a DDC to reclock the data, then output to your DAC. I use a $500 Denafrips Iris DDC, but I'm using a Bluesound Node 130 and just streaming.....not attaching storage like you have. The Iris isolates the USB input both galvanically and optically, and reclocks it with a high quality TCXO crystal.

If you have an interest, check with Alvin Chee at Vinshine Audio.....he'll steer you in the right direction.

sns, 

You are probably correct that someone with your skills could build a dedicated system that performs extremely well. Most of us don’t have your skills, so the standard question remains “will a dedicated streamer outperform a “standard” computer based streamer?” I would suggest it would