One of the reasons Apple specifies a minimum of 733mhz for iDVD 6 MAY have to do with the graphics cards in older computers. There have been reports on the forum of people having problems with the iLife '06 applications and older video boards. In addition, at least on iMovie HD 6, 10.4.4 is required for HD menus. No such claim is made for iDVD 6.
The stated system requirements are here:
http://www.apple.com/ilife/systemrequirements.html
Note that QT 7.0.4 is required.
I suppose the best we can say here is "maybe" it will work for you.