installing and deleting playlists and associated mp3s on iphone

I have converted many of my CDs to MP3s for storing on my NAS. I generally use Clementine or Strawberry to play them. In the past I have used Itunes to copy them to my Iphone, but I would like to avoid that step. Can someone suggest appropriate software that I can install on my Slackware based computer to perform all maintenance tasks?

Thank you.