I'd buy them all, but first and foremost are Aquilonia and Red Nails followed closely by Hyborian Kingdoms and Turan (and please include Khoraja and Khauran in too! I'd love to play out some Harold Lamb-esque Crusader stories). What I was really hoping to see was a Kull of Atlantis Expansion. You could have boards for Atlantis and Valusia and either adapt the Conan rules to play as Kull in the Thurian Age or play as Conan in the sunken ruins against the Serpent Men of Valusia. How cool would that be?! It'd also bring Thulsa Doom into the game while remaining true to Howard's works.