got all 4 2 days ago, will replace a few tonight.
Why bother with replacing fans and not get an aftermarket cooler ?
Aftermarket cooler :
-much cooler so more OC and stability
-easy to work on if fans die ( unlikely with aftermarket fans ) compared to hassle of stock cooler + fan
Depending on the rig, aftermarket can be better or worse. In open frame rigs they are better, in closed case rigs they are worse. I know of no aftermarket fan that routes the heat of the GPU right outside of the case.
Aftermarket kits are usually much more expensive.