DigitalD
Welcome to the AH and hope you have a great experience here.
I'm with
@lovinthehd , the bulk of most system upgrades is found within the speakers. Your speakers are the voice of your system and they have more sway over what you actually hear than any other component. Upgrading your speakers is usually the first place you'll notice the most difference.
Your Sony is most likely up to the job as a power source.
What is it about your current system that you'd like to upgrade? Sounds like a foolish question. But, in order to make sure you actually get a real audible upgrade, its important to know what you're aiming at.
Lots of folks buy new equipment, it doesn't sound appreciably better than their old stuff, so they come here and complain and ask "how come?". Not having a defined problem to solve is the source of a lot of frustration at upgrade time.