If you don't track yours I'm not sure it's worth the outlay. It'll help you hold max power for longer by helping to prevent issues like heat soak etc but It won't give you more power, only prevent you from losing it. Spend the cash on suspension or brakes if you haven't already.
But for info, S3 cooler is fine for stage 2+. I run one at 340hp and have done numerous track days and never suffered power loss or any issues related to it.