Personally, I think you're looking at it from a continuous power standpoint, but the only time it will see that is on your test bench.
Average power is only going to be something like 1/10 to 1/8th of continuous rated.
So, for normal operation your mains fuse only needs survive inrush (unless you are doing rated power sine testing) and short term peaks. Other than that it has a pretty easy average job.
I keep coming back to the rating of the fuse in my ARC 100.2 of 5A MDQ slow blow. This amp has rating of 100wpc @ 8, 200wpc @ 4, and 360wpc @ 2, with the aforementioned 130,000uf.
I think a fuse along that line (5A slow) would be fine for normal use.
If this was a control circuit transformer, I think NEC allows fusing up to 167% of rated primary current for a transformer this size. However, since you have secondary fuses too, it's different. With secondary fuses allowed up to 125% of rated current, the primary side can be fused up to 250% of rated current. Again though, that's NEC for industrial control, not audio amp. That said, NEC is all about safety.