As I said in another thread, I really do need all the power I can get - I do a lot of 3d work, and the rendering is just a wall - with 2d stuff (which I also have to do a lot of, of course), if you wanna tweak something, you can play around, undoing etc, seeing the results instantly. With 3d, you have to render out the image which, when you have complex stuff going on can take absolutely ages - and it's time you can't really use to do anything else, it's just totally wasted. Of course, we'll always find new techy ways of filling up all the CPU power we have, but in theory the resulting image should look better as a result.
As for the blu-ray, I'm afraid I cannot help you that, I have no idea!