>I think I'm leaning toward the D3S. While I shoot a variety >of subjects, most of my work in low light sports.
I haven't used a D800 but I can certainly vouch for the D3s. I too shoot low-light sports and recently picked up a used D3s to replace/supplement my D700. I love the D700, but the D3s really excels at maintaing true colors and natural looking contrast even at ISOs as high as 12,800 or even a bit higher. Here's a sample from the d3s at ISO 12,800 (1/1000th at f/2.8).