I'd say it is possible. "Too Bright" really means too much treble compared to the bass and midrange. the added resistance of a fuse will affect bass and dynamics most since they pull the most current (a fuse has to have resistance or it wouldn't heat up and blow, physics). So fixing the fuse problem will give better balance to the highs.
I'd try a slug first since that is very cheap and represents the most improvement you can get. Your upgraded fuse will not give as much improvement as the slug will. Some power supplies are unaffected by the fuse, others are affected and you might be surprised which ones are which.
Of course you won't have fuse protection for the minutes or hours it takes you to do this test. Don't do it during a thunderstorm.
Jerry