According to [Link: smarthome.com]
The console responds to infrared signals fom the infrared remotes listed above then transmits equivalent X10 commands to X10 compatible receivers in your home.
Well, to me that's a little bit ambiguous, because does "receiver" mean a command console or, for example, a plug in lamp dimmer? Over to [Link: smarthome.com]
and there are items in a category called X10 receivers, which include lamp dimmers, etc. So this leads me to believe that the 4040 IR receiver does NOT require additional models.
Bear in mind, I don't own anything X10, but I'm about to invest. So there's still a possibility that I'm wrong. :P