Good post but Sergio is open to the right hand so I'd give GGG a shot.Im hoping Golovkin gets a big fight should he beat Proksa. When you can it as hard as he can, he has a chance against any middleweight in the world. He's not as good as some people make him out to be, he's slow of hand and foot and he doesn't have a great work rate. I do think the likes of Martinez and possibly pirog would be too quick and skillful for him, but GGG's got the potential to be in some cracking fights with the likes of Martinez, the Geale-Sturm winner (if its Geale ) or Chavez.
For me, Proska is made for Golovkin and he'll get battered. So I'd like to see, in this order of preferability;
GGG Vs Pirog
GGG Vs Quillin/HNDNJ winner
GGG Vs Sturm/Geale winner
Any of those would be great, the best fighting the best might well elevate the current 160lb division from one with great potential to a competitive division of real quality.