For the record, car stereo amplifiers are generally "class A" (linear) amplifiers, and as such are only 50% efficient. Thus if your stereo has a total OUTPUT of 200W it will require an INPUT of 400W when it is at maximum output power. (Which one hopes is never, but I digress...) 400W at 12V (Actually closer to 13.8V if the car is running.) is around 30A. (33.33 for 12V, 29.99 for 13.8V)

The difference between the input and output power is lost as heat. (The power transistors get hot, that is why they have a heat sink.)

Some amplifiers used to be "class B" (Push/Pull) but even those are only 65% efficient. PWM power circuits can be much more efficient but are not normally used for audio amplifiers because they produce distortion.

Yes I know that the "factory" alternator only puts out 35A, and Nissan thought that was plenty, but remember the stock radio had a max output of 6W. If you are keeping your car in "Showroom new" condition, or running a race car (in the day time) then yes, the stock 35A alternator is fine. But for anyone who has added accessories, or off-road lights, they will likely need more power.

I talked to Z-specialties and their 105amp alternators are early gm style that they convert to one wire. They have a shop rebuild them with new vane and rectifier so the unit self excites at 500rpm and delivers peak output at 2100rpm. They have many of these units functioning in cars that are running high rpms like3500-7000 as well as stop light racers with no failures to date. I went ahead and ordered one I'll post again after I test it in the car.