For a top-of-the-line immersive high-def experience, you need surround sound. If you don't already have a set of surround-sound speakers, you can choose from a wide array of 5.1- and 7.1-channel sets. But an increasingly popular option is to use a single-box surround "projector" that tucks neatly under your flat-screen TV. See our buying guide "How to Buy an Integrated Home Theater Audio System" for more information about these space-efficient products.
To make everything work together seamlessly, you'll also need a universal remote. Most large flat-panels come with capable universal remotes that you can program to give you basic control over your peripherals and the TV with a single device. But you may prefer a full-featured third-party remote like Logitech's popular Harmony 880 Universal Remote ($250), which is optimized for HDTV and DVR systems. The Harmony 880 lets you quickly switch between aspect ratios (such as normal, full, and zoom); has a large, color LCD; and supports easy programming through your PC or Mac.