So you get 40 more amps but the fan differences aren't even close to that.The draw of that 850 watt fan at 13 volts is 65 amps.
So yeah, you need a different high amp fuse array.
The 600 watt fan would run 46 amps at 13 volts.
You could at max draw pull 20 more amps.
Premium audio group gets the 220 alternator.It is apparently tied to the premium audio group if you have the 8.4 you should have it