Well based on their forum content at: [Link: x10.com] --- I would suggest NOT the CM15a (I am a former owner).....otherwise, your question is very broad. You need to define what you want it to do for you, with some idea as to how you want to control or program it. (eg. connected to computer running 24x7..or downloaded and removed?) - And what would you like it to do that the CM11a doesn't or can't do for you today?