How do you OC AMD for this coin and for CryptoNight in general. I have 470 mining (giving 3.8 KH/s)  570 8gb (3 KH/s) and 580 8gb(3.4 KH/s). What do you suggest?. And one rig with Nvidea 2.3 KH/s ))

For all AMD I OC Core MHz: 1200 and Memory MHz: 1900 but I think they can go better. Using Simplemining OS