The flexlite type stuff doesn't flow enough CFM in most cases. NAs might be able to get away with a dual 10" or something. There is a Ford truck/van 3spd setup that can more enough air for a TT, but it's not cheap. You're probably better off sticking w/ the OEM fan setup.
Later
More sig fodder:
I'm too lazy to do my own review of AotC. Here's what my idiot friends thought of it. Yes, they did flip off the screen everytime Jar Jar was on it to the delite of everyone around us.
No, I haven't seen Spiderman. I'm too busy doing RIDES pages.