As MarkA says, suspension should be looked at as a complete package.
Lotus went stiffer on the ARB when going stiffer on the springs/dampers when fitted to the Exige. Got the numbers somewhere, but been driving all day! Will try to dig them out.
Logic says if you’re going stiffer again on springs/dampers, then a complimentary ARB will be of benefit. How much, is open to the same debate as spring rates, Nitrons/Gaz/Ohlins.
I have all sorts of difficulty getting the balance of spring rates and ARB right on Gran Turismo!
For a bit of nostalgia can we introduce Scuffham to the debate?! 
Didn’t he swear by hard springs, soft bar?
Ian 
Generally at least once every sentence
There is so much more than just spring rates and anti roll bar stiffness.
A few examples are
Tyre type, temp, pressure, tread depth
Geo settings inc ride heights etc etc etc
Track surface/type/temp
Driver input/driving style
Vehicle weight
and im sure mant many more
What works for one person may not be the ultimate for another.
Hard springs soft bar is tush if you have decent dampers that actually work, in my opinion.
But like you say, all that is probably a can of worms worth leaving the lid on.