Which upgraded fuse is recommended for an Onkyo and Elac setup?

I have acquired a mid grade hi fi system that I am going to put in my office. Its an Onkyo avr priced under $1000 ( purchased sometime in the last year by my brother) with some Elac bookshelf speakers priced around $500.  Not sure of the model numbers. 

In general...which fuse upgrade is recommended?  Trying to squeeze all I can out of this mid fi system. Thanks.