These hybrids are called "Black Forest Conures"... in other words, it has already been done.
If it's a conure, it can hybridize with any other conure. Doesn't matter if it's a green cheek and a nanday, or a sun and a golden... they can hybridize. The larger conures can also hybridize with mini macaws, amazons and caiques.
Not sure yet if the Pyrrhura conures can as well...