I got a cheap asrock pro4 z170 ( like rm 550 ), and my 6600k can go to 4.6 ghz @ 1.28V . The board cant SLI/Crossfire tho.

If u wan make sure u get a good chip, u can buy a binned chip.

Example : https://siliconlottery.com/
I never buy from there before but I google some reviews it seems good. Even a guy shipped to Malaysia with it ( which is ironic because many chips come from Malaysia, shop to US to be delidded tested and relidded i think )