I had a 90 amp alternator in my Jeep and I had to upgrade that. I upgraded with a 600 watt mono amp and a 70x2 Kicker ZX200.2. I was getting a pretty decent voltage drop around 3/4 volume. I picked up a 136 amp alt for it and did nothing else. Now I hardly have any voltage drop at full tilt. My factory alternator was the same output as yours and I was only requiring a little more power than you. You might get voltage drops at full tilt. Now, voltage drops are only bad if they start dipping into the lower 12s because that means your alternator isn't able to keep up with the current demand and it's coming off the battery. If you start going under 11, you have the potential of smoking your amps.