I have no inside knowledge but I simply cannot see the AMEX attraction for a promotor. The transport and catering were both total and utter pants for the Fatboy gigs and I understand it wasn't much better for Rod.
I'm not a fan of Madness but they are incredibly popular on the live circuit and will certainly be a success at the AMEX. From memory the capacity is around 20,000 for gigs. I'm pretty certain this will sell out or come very close if it doesn't.