Using digital TH2G on a 2nd Gen MacPro with Geforce 8800 I can output 6 screens at 1024x768 and 1280x1024. (2 Analog though are finicky).

Using analog or digital TH2G on 1st Gen MacPro with x1900 I can output 6 screens at 800x600.

Using analog or digital TH2G on 1st Gen MacPro with Quatro FX 4500 I can output 6 screens at 1024x768 and 1280x1024