DVD-A offers 1,000 times the resolution of CD and can deliver up to six channels of ultrahigh-resolution sound. But to access those tracks, you need a DVD-Audio player, although almost all DVD-A discs have lower-quality Dolby Digital or DTS tracks that can be played by any DVD player. DVD-Audio sound has great detail and texture, and it's more lifelike than CD. DVD-Audio will be primarily of interest to audiophile-inclined home-theater fans. To enjoy a DVD-A player's full sound potential, you must use a receiver equipped with 5.1-channel analog inputs and good-quality speakers.

The SACD format employs a new technology dubbed Direct Stream Digital (DSD). Proponents claim DSD is kinder and gentler to the music than CD's Pulse Code Modulation (PCM) format. While CDs poke along with a 44.1kHz sampling rate, DSD cranks things up to a warp-speed 2.8224MHz. This results in vastly greater resolution, texture, and detail than CDs. Standard Super Audio CDs will run on only SACD players, while newer hybrid SACDs will play on SACD, CD, and DVD players. To enjoy an SACD player's surround sound, you must use a receiver equipped with 5.1 analog inputs. A good-quality speaker system is required to appreciate the format's potential.

Not a surround format per se, THX strives to deliver cinema-quality picture and sound to home systems via certified products such as speakers, receivers, DVD players, and even cables. Two levels of certification are offered: Select and Ultra 2. Select components are optimized for use in midsized rooms of less than 2,000 cubic feet, and Ultra 2 components can accommodate 3,000-cubic-foot rooms. Also, Ultra 2 is a 7.1-channel system, capable of producing a more uniformly distributed surround effect throughout the room than Dolby EX or DTS ES surround.