the line fuse isnt likely to improve the sound but the internal fuses (the other four) are in the speaker output power path, just as the ones in your dahlquists. in the speakers is a FINE place for the fuses.

i have an adcom 555II which i love the sound of and have given some thought to putting those fuses in the amp. still, the cost is rather high for fuses and they are delicate.

once while playing the LP of mickey hart's DAFOS, all four of the fuses vaporized when the 'beast' hit the floor. POOF, that could be $120 at those prices. keeping a bunch of extras seems to be not cost effective.