I've also got the YN560III and a trigger. For the money it is a superb flash! Get a diffuser too and you're ready to go
Your main focus with the flashes should be whether or not you want TTL or not. I much prefer things doing what I tell them to so being full manual is fine for me.
Another thing to consider is Yonguo are soon to be releasing the 560iv, might be with waiting for that if you're wanting to use it as a flash master.
Very happy with my 560iii though. Get a Diffuser and a trigger and you should be very happy with the results.