To ensure you retain your ratings when you update your legacy Poweramp release, I have provided a backup option in my Free New Playlist Manager app.
Whilst still on the legacy version, simply backup your ratings. Continue to upgrade the latest Poweramp release (V798 at time of writing). You will need the paid for version of New Playlist Manager to restore the ratings.
For more details visit:
http://www.theo.klinkweb.nl/Poweramp.html
or email me.