Thanks! I have a gold champagne mare that carries silver, and I don't know if you know this, but for some bizarre reason, Silvers tend to be AA - which is anathema to someone trying to get Black Silver (the creme de la creme!).
My kingdom for some aa mares! :) - love your tag line too, as it happens!
If we were to eliminate all other components that go into breeding like personality, confo, performance, etc., and look solely at colour, in my opinion, no, double agouti would not be worth more. Colour experts can correct me if I'm wrong, but I believe all the agouti modifier does is restrict black pigmentation to points, such as legs, ears, etc. with the most common result being Bay. I'm pretty sure all that AA means is that resulting foal will for sure express agouti in some way, but since it is so common, I don't think it would be worth anything more, just on its own.