burning a DVD is no different from burning a CD, insofar as you're just burning data to a medium. so your machine can have any processor, provided you can transfer the data fast enough. you should note that you cannot use apple's applications with external DVD burners, but third-party applications such as toast work just fine.
what requires a faster process is encoding DV footage into DVD video... for that a faster processor is a definite advantage.
-r.