Re: X10 controls
My advice is that X10 is a nice starter protocol, but not extremely reliable in the long term. There are better alternatives, albeit a bit more expensive (such as UPB and Z-Wave...stay away from Insteon). Check out some of the home automation forums for advice, and if you really get into it, I'd recommend using a system like HomeSeer as a computer-based central controller.
FYI, you would need an IR543 or something similar to interface an IR remote with the X10 protocol. The IR543 is supported by Harmony.