Bronze vs gold psu? is rosewill a good brand?

hi guys, i am planing on building a rig which consist of 5 gpus of rx 4704gb and/or rx 570 4gb.

a lot of people tell me that it can be done with 850w psu (not ocing too much, maybe to 1870-1900mhz memory and undervolting the core)

can i do it with a 80+ bronze psu? or should i always buy 80+ gold psu?

also is rosewill a good Brand? asuming is 80+ gold

thanks