The Benedini TBS has a library of sounds you can use, and you can load them and change them as you see fit. It as designed for the user to change files as many times as you want.
With the Clark board you can get him to custom build you one, but once built the sound is forever, and you cannot change it. I am not sure if he charges extra for a custom sound set. Freaky can tell you what it will cost to get a board custom built.
My website has details on the Benedini. It is more expensive, but because the sound is programmable it is very flexible. You can even stick it in an RC plane, boat, truck, car, whatever RC vehicle you want to add sound to.
Cheers