Why not upgrade or spend the money on the main system. Instead of selling the used gear start a new system. This is literally how I was able to have a second system. As long as you want or need a second system. That being said I have only been listening to my main system.
Quick System Building Pop Quiz:
Please choose 1 option below and maybe explain why:
1) Make your already very good system even better
2) Start a second system to play with and maybe try something new or different