This is my current setup:

• Corsair Carbide Series 500R
  
• CORSAIR H100 Water Cooling System
  
• MSI R6950 Twin Frozr II 2GB
  
• Intel Core i5-2500K Unlocked at 5.0 ghz
  
• ASRock Z68 Extreme3 Gen3 Mobo
  
• OCZ ZX Series 850W Fully-Modular 80PLUS Gold
  
• G.SKILL Sniper 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600
  
• Asus VH238H Black 27" HD Monitor x2
  
• Mushkin Enhanced Chronos 120GB SSD x2
  

I'd like opinions on what you think I should upgrade and what with.

A better GFX, more memory and a better cooler ofc.

Lmk what you think.

Gtx 1070 as a last hurrah for the poor i5.

I got the cooler and memory. I don't think I'llneed a gfx card that intense.

Why so you need better cooling.
H100 is pretty highend. Do not upgrade that.

Two important informations are missing. What is your budget and what games do you play?

Just clean tour cooler if it needs it.
Buy 16gb ram and a 1070. Should be good.
Could do a 1060 6gb if u wanted. 1070 better bang for buck for sure tho.