If anyone cares... I did try a WS14A with an XPS3 and it works fine. I'm finding that many X10 devices have different part numbers but are the same (I'm sure there is some topic out there that already states this.
So from my experience a WS14A will work with an XPS3 (and likely any other master switch) instead of an XPSS. Obviously no dimming function but that isn't a problem.
My guess is that a WS13a and a XPS3 are the same modules. (As well and as XPDI3)
Actually, we do care - a lot. Thank you for posting your results.
There are a lot of things changing in the designs of the various X10 Switches. New features are being added as a result of these redesigns. Some of the features are nice, some aren't so nice.
If you have the opportunity, could you post the date code of the units you installed. We are trying to keep track of unit releases.