With the XPT line of switches, there is not a recommended module per-se. The XPT is ONLY a transmitter. Depending on the switch plate you get for it, determines it's function. You can get plates that are on-off only, an you can get ones that are on-off with bright-dim. These will control any x10 module that will accept a PLC command. It can also be used with other switches to make them act as multi way (3 way, 4 way, etc...) switches. I have one of these in my living room with 4 buttons. The top 3 are L1, L2, and L3 on-off, and the bottom switch is the bright dim switch.
Also, IMHO, these have a much better tactile feel than the other lower end x10 switches.
Hope that helps.
Dan B.