As others have stated.......if speaker and wiring check out, the SC-01 chip checks out, the amp board is good (I'll add, there's some tantalum caps on the amp board that also go bad).......it starts to get tricky.
First, swap the two custom audio/input/output chips (location X2 and X3) with your Gorf.
After this....it's educated guesses...chip U4, transistors Q9 and Q8, and chip U8.
Edward