['LIVEWIRE?']

Based on years of repairing Blaupunkt and other makes of car radios using Direct Coupled audio amps. of this type I would say that the speaker coupling capacitor is not the cause of the problem. In 99% of these circuits any value between 470uf and 1500uf will work perfectly well. Obviously the working voltage of the capacitor needs to be 10v or higher, and it must be otherwise in good order (low E.S.R. and low voltage loss), but a Vloss of 1% is nothing to worry about. The 4.5% Vloss of C275 is a tad high, but, before I had a component tester which could measure this parameter, all I used to do was check if the suspect cap. charged O.k. on the ohms range of an AVO 8 or other analog meter. That BC328 on the other hand is definitely faulty, and must be replaced. You may find this to be the only fault, since failure of one transistor can cause all the others in such circuits to misbehave. Those BP audio amp. blocks are a bit fiddly to work on, but manageable once you get used to them!