yea the best way is modded the bios to use less power and produce more speed that what's so nice about  these cards now that use 14 NM chips . and they are just getting started ..

you can use afterburner or the WattTool http://www.overclock.net/t/1609782/watttool-a-simple-tool-that-combines-overclocking-with-vrm-monitoring-tweaking-for-rx-400-series but nothing works better so far then letting the card do it self buy modding the bios and doing little tweaks with those tools .