Just some general information and a disclaimer that all numbers are approximate, the bike has a 360 watt rated stator and a 30 amp main fuse, 12 volts x 30 amps = 360 watts, wiring and regulated output are designed to match. A stock bike requires about 250 watts to run. Then theoretically there is about 110 watts in reserve or excess. If you measure your bike voltage at higher rpms you should see about 13.8-14.2V at the battery as this is what is required to maintain a healthy battery, a battery maintainer outputs about 14.5V. As you consume the excess 110 watts the regulator output will begin to drop in voltage, load current will be rising so voltage will be dropping to compensate. You have a set limited supply of power (watts) so as amp demand increases the output voltage will decrease. Most of the aftermarket voltage monitors will go yellow at 12.5V. Any lower than this and you risk not getting started if you stop.
I built a charging system tester that monitors the output voltage and load in amps (volts x amps = watts). I can manually apply a variable load, the tester displays the resultant load current in amps and the voltage level at the battery. On my 1300R I got "about" 9 [email protected]
The voltage levels run up and down a little as you try it multiple times but I'd say you are looking at an average around 9A x 13.0V = 117W. I prefer to not be at 12.5V for hours on end on a trip because at this level the battery is not being brought to full charge. I don't want to be riding in the yellow, I'd rather see "at least" 13V, something above the usual 12.8V a fully charged battery at rest should have.
The equipment in the OP post uses it's own 40 amp fuse. This tells me it will probably run around 30+ amps, 30 amps x 13V = 390 watts. +-360W potential to the speakers and maybe around 70W to run itself with a very good 80% efficiency rating. The numbers are unknown exactly but they will be close. It is impossible to run at this level on the X. The bike has 120W in reserve and the system wants around 400W. The bike voltage would be very low, high power speakers require a minimum amount of power to sound good, you should never run electronics at a brownout level as it generates excess heat, the bike battery will be draining instead of charging. IMO, better to match the equipment to the bike's capacity. Maybe 2 x 30-40W speakers that will require about 100-120W to run the audio system.