Hi Steve,
You can mount and install a repeater at your circuit breaker box. It isn't difficult to install, but it does reqiure working inside the breaker box which has areas that are always "hot" even when the main power breaker is off. If you aren't comfortable doing it yourself, it should take an electrician less than an hour to install one. Here are of the different versions:
http://www.smarthome.com/4823.html
http://www.smarthome.com/4820.html
http://www.smarthome.com/4821.html
I believe that last one is the best, but it also costs over twice as much as the first. I have the first one (Leviton) in my house and it has worked fine for me. Others, however, have had problems with the Leviton model being incompatible with the X10 motion flood light module and the LynX-PLC. If you don't have either of the those, then you should be able to use the Leviton without problems.
Regards,
Matt