I can't speak for BillA, but let me refer you to
this article by myv65. Specifically, check out pages 3 and 4 (it's a very long read). I can vouge for the accuracy/truth in this article, I have verified the information.
That should clear up the Al vs Cu question.
(PS: I still believe that Aluminium is good for a waterblock: it may not be the best in performance, but it will provide anyone with a cheap ability to watercool their rigs, albeit at the cost of a large overclock)
