Tdi Cup sure sounds nice, but AFAIK, it's not a "bring-the-money-and-drive" type series. I don't know what's the deal with 2009 drivers, but for 2008 VW evaluated 54 drivers (of the ones that were deemed worthy to evaluate) and picked 30, based not just on driving skill, but marketing potential as well. According to
this link, it costs $35K/season just to do drive it. Add in the travel expenses, etc. and you end up with waaay more that you'd spend in a Spec Miata even if you go to runoffs. Oh, and with a Spec Miata you can actually
own the car.
As Mattesa duly noted, the runoffs are shown on Speed, and with a relatively well-known (and fairly well regarded) series like SM, the front running guys do not go unnoticed by the people in higher series. I think the prize for SM championship this year was a fully sponsored drive in the Playboy Mx-5 cup.
From what little I learned by reading online, it only takes a few sanctioned trackdays/HPDEs to get a
SCCA or a
NASA licence to race in SE30/SM/Spec944 etc.
Good luck with whatever you decide to do and keep us updated.