Really good ballhead

You say you want GREAT. What's important to you? There are lots of ways to evaluate a ball head. Clever features? Durability? Smoothness of adjustment? Load bearing capacity? Torsional regidity?

If you are seriously thinking of using really big glass, even going as big as 800mm, then those last two categories become very important. You might want to consider this beast:

http://www.naturfotograf.com/burzynski.html

Note: I don't have any experience with it. I use an Arca B-1 and Gitzo 3 Series, or an Acra GP-s and Gitzo Traveler for hiking. But my longest lens is an 80-400.