From experience, KU31 > SS595. You can still pick them up cheap from st george/tempe tyres (Sydney). They last at least 20,000km as well.
Best tyre I've ridden on was a set of used RE050 RE040 are also pretty good. I would actually rate KU31 to having almost the same grip as RE040.
Has anyone tried KU39?
My GT-R came with Falken Zeix tyres, rubbish in the wet. The wheels I put on came with camber worn KU31s, they were better in the wet than the Zeix was in the dry (from memory). I have a set of old 2nd hand Azenis (can't remember the model) at the moment. Doesn't mean that much since it's old and 2nd hand, but the KU31s that I put on before gripped more in both wet and dry.
Street driving only.