According to the PSR-2000 specs, the two speakers in the keyboard produce 12w each. The YST-MS50 has two 20w speakers plus the 40w subwoofer for a total of 80w. The Altec Lansing 621 have two speakers with 45w each plus the 53w subwoofer for 143w total. It looks like the YST is stronger than the internal speakers and the Altec even stronger than that! The Altec lists for $149, but the lowest price is $85. Amazon has it for $108 w/free shipping. I guess I'll have to pass this information on to my wife!