Tuner — At minimum, an AM/FM stereo radio should be included, but it would be nice to have memory presets so you can quickly access your favorite stations. It should also have an antenna for better reception.
CD player — Look for at least one bay, but three would be nice so you are not jumping up every hour to switch CD's. With the market full of options, don't settle for a single bay. A feature that lets you change the CDs that are not being played without stopping the current CD is also worth having. It should also be able to play MP3's you have recorded on your computer.
Dual tape cassette deck — Although most of us have consigned our cassettes to our next yard sale, having a dual deck for playing and recording cassettes is still an attractive option. Look for a real time counter if you are planning to do a lot of recording, as well as auto reverse and high speed dubbing.
Speakers — Check the system's speaker specifications for, at minimum, a tweeter for higher frequencies and a woofer for the mid and bass sounds. Make sure the speaker wires are detachable and not hard wired. This way you can replace them with longer wire if you need to locate the speakers farther apart in the room for optimum sound.
Take a variety of your own CD's along when you go shopping for a system. Listen to a bass guitar sample to ensure there is no "booming" going on, as well as some violins that will point up the treble sound. Then put on your favorite diva CD and listen for a full, free sound. Piano solos will point up any fuzziness. You want to hear a clean, crisp sound.
Most mini systems are two channel stereo systems. However, higher end products offer dolby digital and additional speakers for a surround sound experience.
Equalizer — You may want more control over your audio to customize the sound of your music, and that is provided by an equalizer. Some mini systems try to make it simple for you by offering preset mixes, such as classical or rock, but with huge sound variations within musical genres, this is not optimum audio.
Extra jack connections — Look for jacks that allow a line in and a line out so you can add options like a satellite ratio or home theater on to your system later. You may want to add a TV, VCR or DVD connection down the road. A microphone jack is a great idea for budding American Idols. And while you are crooning, some mini systems have a karaoke feature that minimizes a selection's vocals for your own little sing-along.
Remote — Most systems will include a remote. You don't want to be jumping up from your comfy recliner every time you need to make an adjustment to your system.
Timer — If the system has a clock, you may want a timer to program your system, starting and stopping music to suit your schedule.