I have had 3 mechmans... all were 14.0v hot.
Alts don't do full amperage at the voltage they charge @ with no load, so in reality... I dont get why people get hung up on stuff like this.
Sometimes if it is hot enough, ill be @ 13.9v with dual alts.... only thing that matters is when the knob goes to the right, my voltage stays out of the dirt rather than looking down and going, "look how awesome that is.... 14.5v with no load!"
edit : about the 1600w and dropping into the 12's with a 250a alt and 2 yellow tops??? you should be able to hold 13+ without a battery in the vehicle with that alt and the amp full tilt.