We've been using an Intel Celeron NUC for the past four years. It has served as a Plex client, a (buggy) Steam Home Streaming (now called Steam 'Remote Play') client, and occasional console emulator machine.
It did an admirable job over that time, but it was time for an upgrade. Windows Updates became an annoying – and on the Celeron – a time-consuming distraction. Steam Remote Play was buggy on it, and Plex had announced the intention to deprecate their desktop clients (I was using OpenPHT, which has also been mostly abandoned). Plus, the hardware wasn't keeping up with what I wanted to play on it. It could only play 1080p x264, and anything larger, such as 4K or video encoded in HEVC or x265, would be unplayable.
I considered upgrading to a more powerful NUC or other PC-based solution, but dealing with Windows for this didn't seem worth it, as 90% of the time I just needed an able Plex client. I settled on getting an Nvidia Shield TV Pro (2019 version) via Amazon US (thankfully, before the COVID-19/$AUD exchange rate stuff!). It has the right hardware to play 4K videos, serve as a Steam Remote Play client (a post on that coming soon!), and also possibly as an emulator machine.
The only main caveat is that it doesn't have an IR receiver (it uses a bluetooth remote), but I use a Logitech Harmony 650 infrared (IR) remote for everything. So a little extra spend was needed to get a FLIRC USB IR receiver.
There were a few bugs in the first weeks of using the Shield (mainly colour issues that needed an Nvidia software update), but other than that it's been working pretty good so far. I've decided to still use our TV's built-in apps for things like Netflix, Disney+, and Amazon Prime because the native experience is still a lot smoother. But for everything else, the Shield is now the go-to device.