Does anyone know what setting i need to have on my amp to run 2 power breaks?

my setup is as follows, i have a 50watt valve power amp in a rack. this amp is switchable either 4 OR 8 ohms. the 2 cabs are 8 ohms EACH.

i cant use 2, 8 ohm cabs with One power brake but i am told by marshall that i can use 2 power breaks, one on each channel with these speakers.

however, what setting do i put the amp on?

senario do i put each channel on 4 ohm load, with brake's and cabs on 8.

or do i have he amp on 8ohms per channel and the brake's and cabs on 8?

figero