On first glance I'd skip the vagabond and upgrade the B800's to Einsteins, you will not regret it and the resale value of Einsteins is very high if you don't get on with them.
If you do that you can also swap the $70 CSR's for the $30 CSXCV, which are much better anyway.
I wouldn't get two PLM's either, I'd mix it up a bit with either the $80 white beautydish or an octabox. The PLM's don't offer the control the smaller modifiers do, and the fun of having control over your lights is that feathering.
Compared to the 600-EX-RT's the power from either the B800's or Einsteins will give you much more control. Don't forget most of the time you have a third light too, the ambient, that you can integrate, either as the key, a fill, or a rim light.