Plexamp has completely replaced streaming services for me. Plex will now sonically scan any music you add and is able to give recommendations through Plexamp for sonically similar tracks, and also use that data to build mixes based on mood and style.

There are all sorts of auto generated mixes that Plexamp will make on it's own based on the music you have. You can also make a playlist of say, your top 20 tracks and when the playlist ends Plexamp will just start playing songs that match the sonic theme of what you've been playing so far. Note that I say sonically similar rather than of a similar genre. I love this because genres are often very subjective, and while Plex does take into account the tags you've given things, it also will group songs based on how they actually sound. You can control how many degrees of separation too if you want to keep the theme close to your playlist or just let it wander through your collection.

For me at least, Plexamp is every bit as good as Spotify. My music collection has grown to around 20,000 tracks over the years and it's pretty easy to get stuck on the same handful of artists. Mixes and auto playlist generation in Plexamp has helped me rediscover music I forgot I even have.