I want to replace the stock speaker in my MG100dfx 1x12 combo. The back the amp says 4 ohm (I wrote Marshall and they confirm 4 ohms) but I want to know if I can replace the stock MG speaker with a HM75 Warehouse Guitar Speaker and they only carry 8 and 16 ohm speakers. Can this be done considering the difference in the ohms? Oh and since Im on this topic, I also sometimes run that amp through my 8ohm 2x12 Avatar cab and it sounds great. I disconnect the internal speaker wire and then just use a good speaker cable to hook it up to the Avatar. Is this ok? because on the back of the combo it says "minimum total Imp. 4 ohm".