Should be OK, how much power does the monoblock and 4ch. amp put out (RMS)?
You should be right if the mono is around 1000wrms and the spk. amp is around 300wrms (4x75).
Either way I would personally upgrade the earth wiring at the battery, preferably using 2awg or bigger cable. Replace the stock earth terminal to body cable, add another one going to the strut tower bolt etc. Also add one going to the engine block.
This will improve the charging system, most of the time it reduces the common problem of headlights dimming with bass notes.
I will add though its probably obvious but dont play the system at more than half volume for longer than a few minutes with the car off.