You can even set the DVI-Tag in the ImagePro - but I never tried it with 768 x 576 so far...(and I am not sure it is available...)
The ATI graphics cards are quite flexible in their output resolution.

DVI is no option in this application because my signal will run through a video mixer before getting to the LED wall...

HD-SDI is also no option as the LED wall´s controller only accepts SD signals (... and on the HD side you have a 1920x1200 opposed to 1920x1080 situation...)

Thanks for your reply...

Olli