Larry has ethernet built into his house along with cable. But it isn't located by his home theater system, where he wants it. Would power line networking be a good option for this? Leo would just string more ethernet if he can get into the walls. If he can't, then power line networking would work, although Leo doesn't use it. Still, others have said it's improved, just make sure it's PNA certified.
Another option is Moca Coax, which will let him send data over the coax cable. Comcast uses something called X1 that uses Moca, as does TIVO. Leo recommends the ActionTech Ethernet Coax Adapter.