I get 201MH/s if I am at 950MHz
I get ~150MH/s if I am at 850MHz
try leaving it at 860 to 870 this card and some other 5xxx series overclock generally in a very easy manner.
Don't mess with the voltages in MSI afterburner (btw, I use afterburner too)
- Make a custom fan profile in MSI afterburner (I try to keep the fan around 4000RPMs and the core under 70C)
- Bring down the speed on Memory clocks and you'll probably save like 2Watts, not much considering the card is 108W but it has zero performance impact by bringing it down (plus it's generating less heat this way)
- Expect lots of extra heat if you overclock the card, please again, make a fan profile so you don't ruin your card.