Do you enjoy video games, movies and watching TV? If these activities are important to you, then consider your system a good investment. You can afford to spend more since it will bring you so much enjoyment.
Is the installation for a “man cave” or dedicated theater room? If so, you may extend your budget, since you’ve created a dedicated entertainment room.
Will your system be an important part of entertaining guests? Again, in that case, you may spend more on your system as it will serve as a centerpiece at your gatherings.