Rather than spend time designing and building a built-in entertainment center from scratch, use old kitchen cabinets to create the perfect entertainment center. Like a jigsaw puzzle, you may have to try several configurations of cabinets to find the perfect setup that fits in the space you have set aside. Use materials other than just kitchen cabinets if necessary, such as bookshelves of various sizes, to create the perfect fit. Apply moldings, baseboards and other decorative strips to hide the seams between the different pieces of the entertainment center, as well as give the top and bottom a finished look.
Use a closet you do not need for storage to create a built-in entertainment center. Try to pick a larger closet if possible, since it will provide space for a larger entertainment center to hold your electronics, movies, etc. You will need to remove the closet's doors, the hinges and any shelving or rods inside the closet. Before you start installing the entertainment center, install an electrical outlet in a convenient location, so you can plug in all your electronics once you finish the entertainment center. By placing most of the entertainment center in the closet space, you will be giving up minimal space in the room while still having a deep and large entertainment center.
Under the Stairs
If your living space is adjacent to stairs leading to a higher level in your house, consider building an entertainment center under the stairs. Depending on the size of your television and other electronics, you may need to use all or part of the area under the stairs to construct the entertainment center. As with the closet entertainment center, you need to install an electrical outlet to power your electronics. Once you have installed the shelving, add doors on hinges that can be opened to reveal the entertainment center or closed to obscure it when you are not watching television.