I use lidarr on steriods (it has deemix built in, but deemix seems to have been abandoned. it still works for now though) to download flac, and then I scrobble what I'm listening to with Last.fm. I've found some great new music through last.fm's suggestions.
There's a python application for managing the meta data better than lidarr called beets. You need to be familiar with a terminal, but it has a ton of plugins and options. If you want a GUI, try MusicBrainz Picard, but it's old and not great on really big libraries. For playlist suggestions, plexamp can do that, but only for music you already have.