Dropped frames during playback of 4k/2160p video on Mac mini 2014 I have a Mac Mini late 2014 2.6Ghz Intel Iris 1TB 5400rpm HDD 8GB RAM model. So far it has been great, does everything I need, no issues with performance. I use it more as a media center than a pc. It's currently hooked up to a 32" 1080p LED TV through HDMI.

I'm buying a 4K TV in some time, and just curious I decided to download some 2160p videos, they were very choppy, CPU usage went up to 400% with 20+ threads. It just wasn't working right. RAM usage was around 1.5 GB.

I've tried using VLC and IINA. Currently running on High Sierra.

So my question is if I should try upgrading the HDD to an SSD, as some people suggested me to make it faster? 
Should I be using the Thunderbolt port instead? 

Or is it just time to upgrade my Mac, which I don't really want to right now tbh.

Thank you very much for any suggestions you can give me.

Edit - Problem seems to only occur when I'm using HEVC/H265 videos in 4K, not H264.
The issue is that the the HEVC/H.265 standard is very new, and while there is software support, there hasn't been an update to the Mac mini in a very long time, so there is absolutely no possibility that this has a hardware codec. However H.264 has been around for a long time and there will almost certainly be a hardware codec for this on every device since at least 2010 I would imagine.

Effectively the only way to decode H.265 videos would be for a software codec to use the CPU, and possibly the very limited GPU power in this machine to process this and that is why your computer will be struggling to playback H.265 and not H.264.

There some more details about supported hardware on Apple's website here.

Also worth remembering is that 4K support on most older Mac hardware is limited, and while your 2014 machine supports it, there will be no HDR, and only 30Hz / fps screen resolution on this, further details on Apple's website here.