As it was mentioned by Neuro, The PW setup is it only worth keeping if you are going to use studio lights and want to control the power level on the strobes from the camera. If that doesn't happen in your case, sell all of the PW gear asap.
As far as using 600 ex-rt's, specially for events, I strongly recommend it. Canon has hit a homerun with its radio system. It is super reliable and fairly simple to use, once you get used to the key buttons on the flash (or directly on the camera, since you have a 5D3). We have been using the 600's for almost a year and it has been one of our best investments. We have 4 600s and 1 STE3 now.
My only additional suggestion, would be to consider using another 600 instead of the STE3 as the master. Since you do events, the AF assist light on the 600 is a savior for low light situations, plus the obvious fact that with the 600 you have a flash on top of your camera, giving you another option, beside the slave 600s. In my opinion, the STE3 is useful in more controlled enviroments (which is where we use it), but during a dimmly lit event, you need the AF to work as fast as possible.
By the way, looking forward to the 1.2.1 firmware for the 5D3. The AF when used with the assist light can really use more speed and that is supposed to come with this version.