I can't answer your question, but I can give you some insight.
I actually intend to earn a Masters in Econ and a Masters in Applied Math or Stats (most likely stats). I no longer anticipate the PhD in Economics, although if I were to do so I anticipate I would go directly and forego the masters programs (I will attending in fall 2009 after completing my MBA).
Any legitimate Math program I have seen expect a "standard undergraduate preparation in line with a major in mathematics". I expect this means Calculus 1-3, Linear Alebra, an introductory course in higher mathematics, and probably a few upper level courses (real and complex analysis, probability, diff equations, abstract algebra, etc). I don't see the benefit of a masters in math as many have said here since you need a good background already to apply. That being said, I anticipate being in the 30-70 range if I apply, so perhaps having a masters in mathematics is a good way to differentiate your application to top 20 programs.
Everything I've seen in statistics requires Calculus 1-3, Linear Algebra, a stats course, and usually a programming course. All that being said, I don't see where it helps in the application process, but it certainly could help with the course work or the job market afterwards.
From what I've read here (and you've read it all the same as I have), the masters in math is the best "signaling" mechanism for the adcoms that you have the mathematical rigor to be successful in the program. But I still think that if you have the necessary coursework to be admitted to such a program, you could apply straight to a PhD program.
Perhaps a better idea would be to pick the masters degree that would give you the job you most wanted if you ended up not going for the PhD. Life has a way of changing things on you... I should know, I've wanted to go for my PhD since I completed my undergrad in 2003. It's also why I'm completing the MBA now, as a safety net in case I don't end up going back.