To clarify here -
We had a huge problem a while back with image links from outside sites bringing our server down. Hence we had to disallow those links. The link in the post is an old link I made to post the outside image from imagelink on our forum. Thus it has been deactivated. The original imageshack link is not mine. If you trim down what is in the post to the just the imageshack link URL and sub / for the %2 etc stuff it may get you to the original image. Or it may not, as the post is some eight and a half years old. The person who originally posted the image to imagelink would have to help you there.
If you are matching impedances with an output transformer the impedance of the cans is not what you would use to calculate the cap value anyway. You would use the reflected primary impedance of the transformer you are adding since that is the load the amp sees, and which should be in the proper range for the stock cap value, i.e. 300-600 ohms.