Upgrade from AC68U to AC5300 or AC88U

HI All,

Currently my setup is an AC68U main router and AC68U as an Access Point connected via LAN cable.

I have a WD MyCloud NAS setup which streams 4k video files to a Zappitti media player. Somehow there is always some stutter while playback.

If I upgrade my main AC68U to an AC5300 will there be a perfromance increse in 4k streaming? Or will it not make a huge difference?

Thanks
Sunny