BenFox - 10:50 am on Jan 27, 2011 (gmt 0)
+1 to goodroi and martinibuster's first comments.
Just to throw another element into this discussion wouldn't it be better in the orignal scenario to have a link on the hompeage of the PR6 site rather than on all the other pages?
On a basic theoretical level I would imagine that unless you were looking at 10,000+ pages the actual PR passed from them wouldn't outweigh any reduction in PR from random surfer modelling (which meant that 15% of PR was lost on each link).
On a practical note you might want to think about other metrics beyond Page Rank. I think this video is a good place to start [seomoz.org ]