matthewking
297
The choice is clear...
...ly not easy!
My initial reaction was immediately a Nautilus 3700. I do not think there is any other PP that would better meet your horizontal collecting preferences. But this seems almost too obvious the more I think about it... I also have not noticed many people suggesting a Naut... part of me thinks I'm missing something here! Maybe you already have one? Maybe you've already stated that you are not attracted to Patek sports lines? I dont know!

hmm, suffice it to say that if it were me, I'd be looking diligently for a mint 3700.
If not a 3700, I would be thinking along the lines of a retro 70's Ellipse (or related Ellipse family, like the ref 3782). Similarly, I would consider "the hourglass" line (ref 425, ref 1593, ref 2461, ref 2553/4, etc). There are some great watches here. This "edgy" case direction is a piece to the puzzle that it seems you have not yet explored.
I'm going to throw out a dark horse here --- a 96 in rose gold, and I'm saying this knowing full well you expressly mentioned you aren't looking to expand your Calatrava collection. I know it's small, and I know you are happy with your current Calatravas, but be careful, this little tiger might surprise you!
Happy hunting,
Matt