X2 having to drive it for at least 25 mins constantly, and usually at 61 mph, depending on the car manufacturer, you can learn all the dirty tricks if you get a voltage display to learn and know the behavior of your charging system, every manufacturer will have a different smart charging system, most charging systems in city driving and cars post 2005 as far as I know may keep the voltage under 12.8 volts while driving after the first initial 4 mins of driving it, again it depends on the car manufacturer, idle or stopped is an exception to the 12.7 volt display.
The Best thing you can do, if you drive less than 20 mins every day figure out a combination of things that will keep your voltage at 14-14.4, some cars keeping the air blower on, and parking light on, or simply by turning the head lights on every time, it will keep the voltage above 13.75 volts and under 14.4.
Smart chargers like the Beltran or citek will help a bit but also will not fully charge it to the point to notice a 12.7 volt 24 hr resting voltage.
All newer cars with their ecm's factory alarms etc, pretty much will show a resting voltage of 12.3-12.4 after 36 hrs of resting voltage due to the parasitic voltage drop.
Again there might be some exceptions depending on the car manufacturer, and most of them do not know a system with 4 amplifiers is being used since it's not smart enough to know the owner installed a high current draw audio system.