I have a Leopold FC660C, which comes standard with non-silenced 45-gram Topre switches. It is already more silent than any of my other boards with Cherry mx switches or IBM buckling springs. Moreover, the spacebar is quieter than it is on any other keyboard I have, and the sound of the spacebar is closer to the sound of other keys on the keyboard than is the case on any other keyboard I have. As far as I am concerned, I doubt it would be worth the extra cost for a silent version, which is available for Realforce and HHKB Pro 2 keyboards, but not currently for the Leopold FC660C.