Because you are asking this questions , my suggestion is : use only one psu
Yes you can kill your mobo , your raisers, and your psu , if you are not sure what you doing
Also probably you going to have some problem to set your rig stable with 6 cards setup.
I would go for a 1500-1600 watts psu with a 6 rx 480 setup , just in case if you want to fine tune the cards later for better mining performance