[hdmkv]

There is no best, but for about $150, a GIGABYTE GB-BXBT-1900 ($130 shipped on eBay). Slightly better than a Dell 3050, which seems harder to find now, at a decent price. If you can spring for an i3-based PC, that would be better. I got a used D34010WYK... I see one on eBay for $290 shipped w/120GB SSD and 8GB RAM (not that you need that much RAM or storage).

But, for near $300, you may as well get the ASRock BEEBOX‑S 7100U or 7200 latest-gen Kaby Lake boxes, which do 3D and 4K@60 & 10-bit.

I expect other enthusiasts will chime in with additional recommendations.

Re: 4K rips, they are HDMI capture card caps... actual UHD BD rips don't exist.