Hello Everyone. I need some advice please. I want to purchase a vintage Randall RB-120 bass head (see link to photo, below) and on the back the Speaker Jack states "Output 120 Watts RMS at 4 ohms, but right above it, states "External Speaker 8 ohms"(see link to photo, below). This resembles something I've seen on many combo amps with an extra (external) Speaker Jack, bot not on a head-only unit, such as this, with no speaker. This amp head was not cut away or removed from a combo unit...it was manufactured this way. I am wondering what OHM cabinet I should use to obtain full power....4 or 8 ohm? I was thinking that Randall mass produced RB-120 combo amps and just didn't bother to print a new label for the head-only unit, such as this one. Any help or information y'all can provide will be greatly appreciated. Thanks Everyone.