What is the best system one can make under $5000

Hi,
I am new to speakers in general and have a couple of decent headphones. What is the best system one can hope to create with a budget of $5000. It is ok to include second-hand components as well. It should allow a turntable and at least one optical input and headphone output.

The listening area is 13ft X 20ft.

Thanks in advance for your advice.