Not sure about the issue of your springs being 'soft', but there's a wealth of information here about upgrading. A search will bring up posts going back more than five years, I'd say. Do you know what you have in your forks at the moment?
Racetech have an online calculator for what is considered to be 'optimal' spring rates, give or take, with listings for Street, Race or Dirt applications based on weight of bike + rider. Selecting the model provides for any linkage ratio to be accounted for. The stock rates & Racetech's suggested rates are given for most bikes.
I don't think their knowledge & experience can be doubted & believe other specialists use similar calculations. However there's always a bit of room for a user's riding preferences & standard of road surfaces to be taken into account. For the rough roads here I prefer softer springs, but good damping is maybe even more important then to achieve good handling (in street bike terms at least).
With stock forks I found the Ricor Intiminator valves very effective used with quite light Hagon progressive springs. This was with a ZX9R rear shock.
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