AU xr8 vs Ef xr8

[Longreach]

I'm considering one of the two options, Au xr8 or E series xr8 for my next car. (Rather newer than older so like EF onwards). There pritty much what i want so thats what i'm hunting, but for the questions.

* There much difference in power in the engine??
* How difficult is it to find a decent example of each, like is there a major lack of one or the other in the second hand market?
* Could i get a rough price for each, i have an idea of what i'll be looking at but another opinion on there value won't hurt.

Thanks Pat