Hey guys... need some advice... this is actually a question my guitarist has. He has a combo amp (Marshall JCM800 2x12) and a cab (Marshall JCM800BX 4x12)... he wants to be able to use both, powering the 4x12 with the combo. Speaker Cabs: 16ohm 4X12 (cab) 8ohm 2X12 (part of combo amp) Does he put the 2X12 combo amps power output on 4, 8, 0r 16 ohms? ...or can he not power both, and have to choose between the cab or internal speakers? Thanks in advance.