Hello, first thread post here.. been reading for years. I have retrofit 2 Peavey 115 cabs to fit a BW 15o2-4 speakers, and plug into the external cab jack on back of a Combo 300 to get 300 watts at 2ohm's otherwise, its @ 4ohm's and 210w. My question is can I plug a 8ohm cab into the back...