Can 600ex work with 580ex?
Great. If I can sell 580EX II at similar price, I will sell it.
I sold my 580's on e-bay. I got $390 for one of them and $350 for the other one. That was about 6 months ago. I don't know what they are fetching now. With that money and the $240 or so that a PW TT5 radio would have cost, I figured it was close enough to a wash that I went with the Canon’s. Canon had tehir $50 rebate going on then as well.
Good luck. I am sure you will be happy with the Canon's if you decide to go that route.