One program that may meet the requirements MediaMonkey. Among its features:
- Can handle a large library of audio and video files (over 100,000).
- Can convert files into a variety of formats in your library.
- Can autoconvert files to the desired format when it loads them on your player. As an example: I rip the music from my CDs into FLAC (Free Lossless Audio Codec) and when I have MediaMonkey load them on my player, I have it convert them into the following format: LAME encoded MP3 at the available highest quality.
- It can update the metadata for your files.
- Can work with a large number of audio players, including those from Apple, Cowon, Sansa, and Sony.
- Can autoorganize your files into playlists via criteria (much like Calibre's tags).
- You can sync your files to your player or send them manually.
I've been using MediaMonkey for a while and I've found it to be an excellent program. I liked it so much that I bought the paid version (which has features not available with the free version).
I hope this helps.