If the breaker panel room is something that you will consider as a negative (can't install a phase coupler), then you can do what I did. My breaker has no room, but there was space around there... I went ahead and purchased an external work box to mount the wire-in phase coupler and a pipe to run wires through. Powered off the mains, installed the box nearby, ran wires from each phase to it, and presto. The work box is sitting below the breaker panel, behind the wall - and this is an external breaker panel... Looks like it could be an external covered outlet to any passerby...
Of the various technologies, I went ahead with UPB - it might be a bit more expensive than some other power control methods, but for the reliability, functionality, and knowing that most people support it now, it's well worth it. Haven't had a single problem with the install. You should also take a look at the Premise Home Control software (check the other sub forums here) as I just started using it with my UPB setup, and wow, the amount of control you get with this formerly commercial software (now free) is just amazing.
