The 9590 is, for all-intents and purposed, a heavily overvolted and overclocked Vishera chip. It might have marginally more headroom than an 8320, but all-in-all the experience will be similar. The 9590 may be more hand-picked from a particularly solid stepping, but other than that it's like buying an OC graphics card, you're paying for someone else to do something you already know how to do, and enjoy.
All that being said, an H100i or Kueler 240 will be the lowest watercooling you would want if you want to match the 9590's speeds (or use a 9590). I have found this H60 works fine for clocking my Wishera to 4.3 without too much overvolting, but if I go much higher voltage-wise it can start to hit 70C, and I'm not comfortable running it like that long-term.