Coltrane,
I recently popped for some Hi/Fi tuning fuses from PCX. Unfortunately I haven't had the chance to evaluate them, when I do I'll post a comment. I only bought these due to recent reviews from some BH's. That said I have to believe that the difference is subtle, like, it seems, with many "upgrades". I'll admit I'm guilty of making some changes in the past because I had the money and I just figured "why not" . Not the best path but one I'm learning to be more discerning with. Subtle changes IMHO can take time to detect and for me that requires patience which I'm also learning more about these days.
Regarding the fuse size, of course I would recommend staying with the 1.5 amp if indeed that is what came with the Stereomour. I'm sure you realize the value there was selected to protect the downstream components and while you may be able to get away with a 1.6, should a problem arise you risk replacing more than just a fuse. Standard fuses are cheap. If you are considering a boutique fuse at 1.6 because the 1.5 isn't available keep looking and be patient. The fuses I got from PCX were about $40 each, so $120 to upgrade my gear. The question for me is: where does upgrading the fuse fall in the que as regards audible changes. I do not have that answer yet. I'm sure many forums will post glowing results. Please be careful with those evaluations as your gear and ears are most important.
Kind regards,
John