The CTK-691 doesn't have a Smartmedia card slot and the speaker system is only half as powerful as the WK-3000 & 3500 models (3 watts per side instead of 6). For an additional 100.00 I think the WK-3000 is well worth the extra expenditure. Especially with all the extra data that Casio has made available for download, it would be great to be able to store it all on a Smartmedia card, along with a bunch of MIDI files. The onboard Flash memory is only about 1.5MB.

Hope this helps!

Michael