Ironically, it is the lower end CTK5000/WK-500 that has the sampling function. CTK6000/WK6500 and CTK7000/WK7500 do not.
There is no download site for the 7000 series sounds, and while the rhythm sound downloads for the WK3500 can be used from the site, the tone library does not work.
Having said that, your WK7500 is pretty much loadeed with every sound Casio could come up with.
Rememebr that the sounds are programmable and can be saved in the user tones area.
Also, if someone has done a great set of user tones, they can be saved to a SD card or PC as a TN7 file and loaded onto other units (haven't seen a swap site for TN7 files yet!).
The Y-man