It's a lot better to identify the problem before you go trying to fix it. If you try to fix theoretical problems rather than focusing on ones you can actually hear, you're going to end up getting theoretical improvements, rather than ones you can actually hear. It really isn't hard to put together a great sounding system. If you do your research correctly, you should just go out and get something and use it until either it burns out or you do. If you're replacing stuff you've already bought with something different, you're doing it wrong.