Hi Palliser,
I'm currently designing a SAM3X8E Arduino "work-alike" system and was planning to use a W5200 but this thread has convinced me to at least break out all the EMAC signals so I can add the PHY at a later date.
Thanks for you work in this (and other) areas, I also have both CAN interfaces on my backplane so will presumably be looking to your work there as well.
Rob