HSTuners - alternator output 92 civic

Hey,
i have a 92 civic lx 4dr
i'm going to be puting another amp in and i'm wondering if i will be drawing too much from my alternator

currently i have a kenwood mono amp running a 10"
it's specs show that it draws 15amps
i'm looking at adding a 4channel pretty soon
about the average i've seen for specs on some amps i'm looking at is around 35 to 40 amps

my question is if a stock civic alternator can put out 50 - 55 amps without messing up any of the other electrical systems

i've heard that you are supposed to estimate your alternators reserve as being 40% of it's total capacity
this would mean that my alternator has to have a capacity of around 125 amps in order for me to run those two amps

any help or advice would be appreciated
thanks
Sean