I would check with the manufacturer, but IMO the fuse rating with an amplifier like this should be set (not pun intended) to be just slightly above the AC current draw that the amp has after one hour of operation. You'd have to find that out with an AC amp meter so unless you have the equipment, it may not be that easy to sort out.
One fuse controlling two channels complete with filaments might actually be that high. It would not give you a lot more than just fire protection though. I guess I am used to using a few more fuses in the amp to give greater protection.