Suggestions for a good Android music sync app?

I've been searching for an app that can take my iTunes library, and sync my music onto my Android (HTC Sensation, running ICS 4.0.3), but not all of my music, just the music I choose. And I sound demanding, but I want it to actually sync, as in, if I plug it in again because I've got some new music I want to move to my phone, it doesn't move all the music all over again, giving me two copies of every track I had on my phone before.