Don't spend money on a bios, very easy to do yourself.

http://www.overclock.net/t/1604567/polaris-bios-editing-rx5xx-rx4xx

I use the uber mix on my rx470 Samsung, it does 28 to 30 now.

Just follow the instructions and don't forget to use pixel patcher once you have modded your card, or the drivers will not work correctly.... Also back up your original bios, I could do a basic mod on a card in under 5 minutes theses days...