I think the absolute best one out there that I've used is Helium Music Manager 7 Network Version 7.3 which the Network Version part is the highest pro version you can go. Unfortunately, the program costs $50 for you folk who still want to pay for things but it was free for me of course cuz I got mine from
warez web-site which the downloading of the program includes the serial number. Anyway this program has everything I ever wanted AND some!
You can sync to iPhones and other portable devices, stream access to the music via another pc in your home or halfway around the world, tag digital media and media that hasn't been in use since you were a kid like cassette tapes and vinyl records, convert to different formats and bit-rates, and the use of a strictly iPhone/iTouch-only app to control the media from your iPod/iTouch. This is just to name a few too.
For more info:
http://www.helium-music-manager.com/compare-versions/
P.S. The Helium Music Streamer to stream to any location is reported to be not that great on the site's forum so if you're looking for a decent streamer search for one on google or go here: subsonic.org/pages/index.jsp
Enjoy!
