No doubt that wise modification choices can improve the sound quality of your Onkyo amplifier but only to a certain point. As has been mentioned the speaker plays a major role. I would ask what is your ultimate objective? If you’re willing to spend up to 10 K dollars for an integrated amplifier you have a multitude of wonderful choices available to you. What type of music do you listen to most often? With proper planning and execution you can create a superb system. The key is to define what you really want. There's a lot of excellent sounding components available out there.
Charles,
Charles,