This is result of inrush current, I had the same issue with my Coincident 845 SET amp and former Cary push pull. I went up a couple values both times, no more failures. My take is as long as fuses are blowing they are doing job intended to do.
Perhaps they are undervalued to whats stated on fuse. If they are blowing on startup, they'll also blow if equipment suffers some other failure.