PC Master Race

Hey all. I'm currently renovating my basement and have been thinking about finally creating a comfy couch gaming setup. One of the many options I've been mulling over, besides running Steam Link over ethernet (~ugh, that lag though!~ lag actually wasn't that bad, but for some reason I can't get Steam Link to adapt the screen resolution to my tv) and running a RUIpro HDMI cable through my walls from the tv to the rig in my office, is maybe moving my 3080TI into a new SFF build to serve as a PCMR steam console for the basement. Preferably something small and nondescript, yet powerful enough to comfortably drive my 3080TI. I would stick an xbox adapter in it, hook it up to ethernet and my 4K TV via HDMI and call it a day. Bonus points if it can double as a blu-ray player, because why not.

If I am going that route I would like to not spend too much, so I was wondering if maybe I could just pick up (from eBay) a prefab with a removed GPU, since that used to be a thing a year or two ago. Is that still a thing? And if so, can you recommend any specific models that would work well in my use case? Or did I miss the proverbial boat and am I better off just building a new SFF unit?

Any and all input appreciated!