I've been using X10 for 4 or 5 years now. My home is about 4,200 sq ft and as I started out, I could only reach 1/2 the house with about 75% reliability. I tried out the Signalinc coupler repeater, plugged in to the upstairs dryer outlet and it increased coverage to about 3/4 of the house with about the same level of reliability...maybe less. The Signalinc seemed prone to producing firestorms that would drown out plc signals.
I then tried the X10 XPCR and wired it in to the main panel. It was less than useless and I'm thankful I only paid about $20 for it from one of the Ebay dealers.
About a year ago I bit the bullet and ordered one of the XTBIIR units from Jeff V. WHAMM what a difference! I now get about 98% coverage to the house with about 98% reliability on the signal transmissions.
To my mind, the XTBIIR put the FUN back in X10.
I installed the double pole breaker and wiring myself. It's not rocket science, but does require some caution when dealing with wiring. Not sure if this is any help, but here's a (crappy) picture of my installation. I ran wiring from the service box to a gangbox next to the service panel, and from there in to the XTBIIR, which you can see in the lower right hand corner of the pic...