Is Ayinger's yeast available from one of the major yeast houses?
WLP833 is said to be the Ayinger yeast, and that seems possible.
Is the Jahrhundert a Dortmunder or a Helles? I was under the impression that it was a Dort and Morty's description up top says it's an "EXPORT-STYLE". I suppose it's possible that some Dorts are very helles-like these days.
A lot of places seem to call it a Dortmunder, but I think I'd call it a Helles and it won the World Beer Championship as a Helles.
The best Helles is probably the Andechs, while DAB is the archetypal Dortmunder (though not my favorite). Since you can get all 3 in the US, these days, you could compare them side by side to see what you think. I'll have to try that, but I'd say the Ayinger is closer to the Andechs than the DAB. On the right day, I might go the other way, I suppose, since they are not hugely different styles.