Here's a little more info;
The '72 catalog says its 150 watts RMS, 350 watts peak.
They suggest a myriad of speaker combinations;
One or two 6X10 cabinets, Sunn Transducer (CTS?) drivers.
One or two 3X12 cabinets, Sunn Transducer (CTS?) drivers.
One or two 4X10 cabinets, Sunn Transducer (CTS?) drivers.
One 4X12 cabinet, Sunn Transducer (CTS?) drivers.
Two 2X12 cabinets, Sunn Transducer (CTS?) drivers.
All 10" loaded cabinets were available with upgraded Sunn "Magna" drivers. (got me!)
All 12" loaded cabinets were available with upgraded (Cerwin) Vega drivers.
Member loudthud has painstakingly put together a helpful catalog guide by year.
http://sunn.ampage.org/sdp/index.php/topic,4178.0.html Here's my speculation*. The Concert series is a very revered solid state amp with sought after built in distortion. It produces a solid 150 watts into a 4 ohm minimum load (the later Concert models are rated to 200 watts into a 2 ohm load, but there is some questions about the amps longevity at 2 ohms).
*Uhmm... You transistor guys can jump in any time now…