I use the X10 XPCR Coupler Repeater Amplifier in my present house and it
works very well. That said, in my previous house I order the same unit,
installed it and it was a disaster. It would send out random X10 codes,
apparently based on noise. I got an exchange unit and it did the same
identical thing, so I returned it and went to the passive unit, 4816H
SignaLinc Hardwired Signal Coupler. It worked ok, but didn't do
anything to improve signals getting to far off parts of the house. I
don't know if X10 improved the XPCR design or it's just a different
house in an area with less noise. I know for a fact that the power in
this new house, western NC mountains, is pretty dirty, compared to the
old place in suburban Chicago. As to noise, I'm guessing that with
fewer people, scattered about, it is quieter, even though regulation,
reliability, etc. is much worse.