Thanks for sharing your nice, sporty collection. As others have noted, I think you should invest in a box with wider slots to avoid scratches on your beauties from the watch cases rubbing together. 
You said you were thinking of adding an IWC. Which one? The Aquatimer or Vintage Aquatimer?
How about an Audemars Piguet Royal Oak, Royal Oak Offshore, or Offshore Diver?
Vacheron Constantin Overseas?
Patek Phillipe Nautilus?
Blancpain Fifty Fathoms?
Piaget Polo FortyFive?
Glashutte Original Sport Evolution?
All the above would be at home in your sporty/elegant watch box!
Cheers,
Daos