There's a lot of considerations that can determine which direction you may want to go.
How does your system sound to you now? What do you think is lacking? Is your system used as part of an A/V system or just for listening? Are you looking to upgrade with new or used equipment? Is space a consideration if you decided to upgrade to a larger speaker system?
You're looking into a deep rabbit hole - how much money are you willing to throw into it?
Sorry for all the questions, I know you're looking for answers. But the more detail you can give, the more focused answer people can give you.