the SACD stands for 'super audio' cd.. i am not an expert, but the basic concept is they remaster a 2ch cd into a 5.1 multi-channel track. to get the FULL or REAL effect of the 5.1 multi-channel mix, you MUST connect the dvd/cd player using the individual component connections for each channel(fronts, center, surrounds, and sub). the quality of the sacd depends largely on who mixed it and how it was mixed, but in general, the SACD sound experience is much better and more enveloping than your basic 2ch original.
as far as the SACD disc and format, when purchasing the SACD you need to ensure if it is a 'single' layer SACD, or a 'dual' or 'multi' layer SACD.. the difference is the 'single' layer will ONLY have the 5.1 mixed version of the tracks.. it WILL NOT play in your standard cd player, only players that are SACD equipped. the 'dual' or 'multi' layer SACD have not only the track mixed in the 5.1, but also the original enhanced 2ch standrd format. these types of SACD's will play in ANY player. but, if it is put into a player that is not equipped to play SACD's, then it will ONLY play the standard 2ch mix, and not the 5.1 mix.
hope that makes sense and clears up some of your questions.
bigjohn
