Alternator wise I always recommend 4 different companies of which i have personally used and or clamped for output and all do at or above rated...
Around 240 amps is the most that can be done on a small6g case such as the focus
now Mechman use to make a Big case kit for the Zetec Focus which can support a large 6g case capable of 270amps +
I am currently on a stock alternator which is ok for burp situations...but I have a 200A Tenny Alternator ready to be installed ..Just trying to decide on what i want to do system wise first
Current : 2 15s 149.5@56hz 2k rms Previous Trunk box 1 18 ,146.4@43hz 3500rms,Sony 12s 145.6@63hz