Re: upgrading to newer roku device because old one no longer supports amazon prime
A new(er) TV with HDMI will produce a better picture with modern devices (Streamers, DVD, bluray, computers, screen mirroring sticks etc). Unless your eyesight is poor you will notice the difference.
Or stick with a Roku 3 which did get the 10.0 software update but will be slow.H
HDMI to Rca analog adapters are very hit and miss. This is deliberate because of copy protection protocols that are part of HDMI standards, the device wants to "sense" it is connected to a compliant TV device.