I have no idea who James Spader is sorry! So I'm really going off topic here, but I recently read a lot of critisism about Benedict playing Smaug, especially that his voice is not 'deep' enough to be dragon like. Which struck me honestly, because he has one of the lowest/deepest voices I know :O

I personally think he's a great choice for Smaug, he really surrenders himself to the roles he plays, he will do fine :)