The WS13A and XPS3 is the samething. Those rocker switches fit into standard rocker plates available at Home Depot. As previously mentioned, those rocker switches need a neutral wire. Make sure there is one in your outlet box.
Once all is hooked up, those rocker switches make a "thunk" noise when activated on/off. So don't let the noise startle you.
You will enjoy getting the automation going. I'm sure you will have many questions getting things setup. Search the forums for any problems you may encounter and don't be afraid to ask for help here.
IMPORTANT: Once you get your software installed and the CM15 plugged in. Setup an appliance module in the software. THEN, plug that module you bought into the outlet in the room you want to control and then plug a simple lamp into that module. Then test to make sure the computer can turn on/off that module. Do this before you start wiring up switches. Reason being is that some houses are in two electrical phases and the signal to control can't jump phases without some modification add on. Doing things with this simple test shows that all is working as far as communication, so you don't think you wired the switch wrong.
So, once you get your software. Start a new module, make the code whatever (ie L1). Then on the actual module turn the dials to house code L and unit code 1. Plug into wall, plug lamp in (turn on lamp). Then check by using software to on/off module.