A 5 year processor might be a tad old but definitely worth trying it before you buy it as it may well work.
You only need high end pc's to run 4K games, streaming TV is far easier (most tv and movies only run at about 30fps ish) so I think if you can't run it now either a cheap graphics card or a processor upgrade and you should be fine.
If you want 4k at a decent refresh rate (60hz) then your going to need a graphics card with HDMI2.0 output and is HDCP 2.2 certified, otherwise your only going to get 4k at 30htz, and on a pc on a decent screen that's really painful, mouse is very jerky and no smooth movement.
Are you running the PC through an A/V amp or direct to the TV, if running through an AV amp then guess what, your going to need to upgrade that as well to one again with at least 1x HDMI 2.0 out put and HDCP2.2.
One final point there is at the moment only 1 4k Blu-ray player for the PC that that's the Cyberlink Power DVD (latest version)
Emby Server / Theatre and Kodi are options if your using the pc as a Home Theatre PC (HTPC).
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