I once asked Alan Frew about them..
He didnt say too much but suggested that $500 would be a good price for a second hand single group. *
I get the opinion that Alan is not the sort of guy that cracks nuts with a sledge hammer where as I tend to back over them with my sherman tank.
Check the a.c archives, I think I found a couple of posts there. *Someone from Aust. had one.
Gidi - has one from the post in the recent thread.