Here's a plot showing roll gradient (°/G) over three laps.
Green- Stock springs, stock bars
Red- 400 lb springs, stock bars
Blue- 400 lb springs, Whiteline Bars (3X & 2X stiffer than OEM)
This shows the effectiveness of springs and bars fairly well. Increasing spring rate by a factor of 2.5 or so dropped the roll gradient by what, 30%? If your springs were only 30% stiffer, your roll gradient would hardly be affected.
Considering you're looking at this from a street perspective, I think you're going about it backwards. Bars will allow you to corner flat while maintaining compliance over bumps, whereas stiffer springs all around will handle everything like a skateboard.