Hi Carlos, the integrates circuit series STK412-XXX it's conformed by 8 integrateds that works with the same conection diagram and the sames components, even the asignated pins, in this case, 22 pins. These are the terminations and their specifications.-090 50W+50W 37V @ 8 ohms-000 60W+60W 39V @ 8 ohms-010 70W+70W 43V @ 8 ohms-020 80W+80W 45V @ 8 ohms-030 100W+100W 51V @ 8 ohms-040 120W+120W 54V @ 8 ohms-150 150W+150W 57V @ 6 ohms-170 180W+180W 55V @ 4 ohmsAs you will notice, they change their potency and the feeding voltage.About your question, the difference between the 150C and the 150M is that every circuits factory uses a different letter to tag their products, also the stores add some logo or letter to recognize that circuits sells. Tecnically, in their interior, they are the same, maybe the quality of some components or their useful life varies, but it will work the same.Now, you're saying that you have two devices, one with 2 audio outputs and the other with 4, I couldn't check the diagrams but maybe the 4 outputs device have the two outputs in parallel, I advise that you follow the tracks on the printed circuit and see if they are connected to the same pin.The output pins are the 8 and 9, passing through 2 resistances for the first channel, 10 and 11 passin through two other resistances.I hope I've been helpful. Goodbye.