Okay I will accept that I probably only said Nathan as I recently watched him in Dr Horrible and thought he did a good job not to mention being bulked up a bit.
As to young actors I don't think I know of any who would fit the bill.
Possibly Joel Edgerton XXXX actor
Damn it is hard to think of someone tall imposing and cute all in the same body.
And thanks for the welcome. I have loved Terry books since I stumbled across the first one many eons ago. They have a whole shelf in my library dedicated to them. One day I will meet the man
But I think I would picket to get Brian in as Ridcully.
"The two most common elements in the universe are hydrogen and stupidity." --Harlan Ellison