I upgraded the fuses in my MX-Rs to positive effect. How much you notice will, to a large extent, be determined by the resolution of the rest of your system. In my case, there were 10 fuses for a cost of $450, but I felt it was worth it.
Upgrading Fuses
Have a Audio Research Ref 3 and am considering upgrading the fuses but I am a little skeptical. Would like to hear from people who have try this. Hard to believe that fuses can make a substantial difference like the manufacturers claim. All advice appreciated.