The dampers actually should have different stiffness front and back. The spring is the same, but the rear damper operates at a 5:1 lever ratio, the front is less, and then there is the mass distribution to take into account. You most likely want to start by having the back maybe 50% harder than standard, and the front standard or thereabouts, and adjust towards harder in small increments having seen how it drives. Then when it feels right, leave the front alone and adjust the rear up or down a bit. That way, there is some sense to the adjustments, instead of just randomly trying things, so you ought to get to the final result quicker.
Too hard is pointless, and will actually reduce the roadholding, although the handling may perversely seem to be better. But it is your car and your driving style, so really only you can finally decide what suits you best.