Aaron, as the previous replies indicated, the least likely reason for a difference in sound between the sound which you're getting(which you describe as "good sound")and your father's is the receiver. Certainly a Yamaha isn't superior to a Denon(or vice-versa). Consider all other aspects of the setups, not the receivers, except if special sound processing modes are in use with one or the other.

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Enjoy the music, not the equipment.