JRiver Media Center has the
Play Doctor function which is somewhat similar to iTunes Genius. You enter an Artist, Genre or Song and it builds a playlist based on options of Some Variety, More Variety or Lots of Variety as well as any inclusion / exclusion rules you have set. Generated playlists can be saved with single click Radio buttons.
JRiver does not have Apple Airplay, although third party Rogue Amoeba's
Airfoil app can be used in conjunction with it. Although I have Airfoil and do use it to stream browser content to Airport Express, I have opted to use both JRiver
and iTunes - JRiver as the main player and iTunes for Airplay streaming to three Airport Express locations controlled with iTunes Remote app on the iPhone, iPod or iPad as well as syncing to those devices.
Files are imported into iTunes and JRiver is set to simply monitor the iTunes library folder location. Because iTunes doesn't play FLAC files, any FLACs that I had were converted into ALAC or AIFF.
Steve