So now that I'm playing full time in a loud rock band again I'm finding that I could use some more stage volume. I have been running my Markbass CMP121 combo (same head unit as the older LM II, 1x12 8 ohm internal speaker that can be unplugged externally) together with a 1x12 8 ohm extention cab. I just got my old 2x15 4 ohm cab back that I would like to run under the MB. I tried it at practice for a short spell and it sounded freakin great. I'm worried though, that at higher stage volumes and for longer durations the 2.66 ohm load will let out the magic smoke from the MB. Acording to the MB manual, the amp puts out 300 W RMS at 8 ohms and 500 W RMS at 4. Of course, they say don't go below 4. So my question is am I really gonna let out the magic smoke? If so, can I up the load on the 4 ohm cab by putting a 4 ohm, high-wattage resistor in series with the cab? If not, should I consider rewiring the cab to 16 ohms and deal with the drop in output (will I still get a volume gain VS the single 1x12, 8 ohm extension cab)?