considering this upgrade purely for improved sound quality. But will spotify continue to use the 160kbps files in cache even after upgrading? and if so should i delete the contents of the cache folder? Would it be safe to do this after logging out and closing spotify completely - as i might do this after the upgrade just in case? Thanks.
I am not really sure to be honest! I would say it must overwrite the content at the higher quality.
But yes to be safe I would get the cache location from Edit/Spotify > Preferences > Cache and just delete that folder with Spotify closed and then it will definitely download at 320kbps providing the High Quality Streaming option is also ticked.