Try the one it came with!
Seriously, I think it's the best they've supplied on the GS so far. I rode out to the Saxonring MotoGP, in the former East Germany, in the summer with no problem at all.
My 2006 GS had a painful joke for a saddle causing me to go the Sargent route (after being rescued by the Air-Hawk as an interim). The 2009 seat was an improvement over the 2006 effort but not as good as the Sargent. But the 2013 seat is virtually as good as the Sargent so I'm not looking to invest a serious amount of money on a marginally better saddle.
As for the Air-Hawk (an excellent piece of kit I have to say) I would expect the model quoted for any of the GSs would do. The unit is not tailor made rather it is a universal fitting with only a few variations in size/style available.