[noggin]

What about in terms of HTPC..
what is the lowest CPU do you recommend that can do this?

Also is there any second hand dell or lenova SFF PCs etc that can do this? 

I like to consider all options... 

A lot of people have switched from Intel/AMD HTPCs to ARM-based boxes because HDR support, and reliable HD Audio (which for years was a given), become a major issue with Intel/AMD/nVIdia PC solutions. Quite a few of the former Intel/AMD platform Kodi developers have either retired from active development or switched their interest to ARM platforms.

There is some HDR support now - but because Intel took forever to implement HDMI 2.0 native support on their SoCs (they relied on a Displayport to HDMI solution using an LSPCon to convert between the two standards, which itself needs firmware updates quite often) the conversion often caused issues with HD Audio bitstreaming and HDR support. Driver support in Linux vs Windows was also an issue. (Some things work better in one OS than the other)

Make sure you check out HDR and HD Audio support specific to the box you are buying AND the OS you will be running.

One major reason for the Intel/AMD -> ARM switch for many is that the ARM SoCs are developed specifically for the Media Player market - so support for Media player functionality (HDMI 2.0, HDR, HD Audio etc.) is their prime focus, whereas for Intel and AMD, it's far less of a priority compared to laptop and desktop day-to-day computing functionality, so their focus is less specific (and development of new functionality seems to lag)

I'm not saying HTPCs are bad - but they are no longer as dominant as they were 10-15 years ago.