A lot depends on how many users you expect and how much media you expect. For one or two users with that stack, transcoding media is really the only CPU load. If most of your media is already in your desired format, then that’s not a big deal.

My stack is pretty similar (no *arr, plus tvheadend, homeassistant and a kodi frontend) for two users and it sits near idle all day long. It runs on an N100 NAS system off Aliexpress with 16GB and will transcode 1080p to x264 at just about playback speed… System runs from a 100 GB nvme, with a couple half-full 4 TB WD Reds for data. 35-ish Watts, maybe an extra 5 when actively transcoding. Used to be ~150 USD,

If you want a lot of 4k content, then I’d definitely go with the GTX 1660.