To op poster,have you considered using the parallel mode it produces p=x2 as well but you need to have Zspk/2 at the current taps of the transformer,this means your current spks won't produce p=x2,please note bridging produces p=x4 when v=x2 into your current spk which means the amp power specs are exceeded the max is p=x2 (1 amp max p + 1 amp max p = px2)
try parrallel but use spk with half the impendance of you current ones for p=x2,also the wiring is simpler with xlr
cheers