One thing that you can do is to just nicely ask your wife to put one of these on before she goes to bed.

http://www.amazon.com/Peltor-H10A-Optime...2771&sr=8-1

http://www.amazon.com/Peltor-97079-Comba...2771&sr=8-7


But, to be serious though...My wife goes to bed before me and the master bedroom is right next to the living room (where I have my home theater gear). Right now we don't have the funds for any kind of sound isolation solutions in the living room. So what we do is make sure that the bedroom has some kind of white-noise being generated, whenever the other one goes to sleep. For example, we have a humidifier running in the colder months of the year (which we would naturally want anyways to help with the dry air, when the furnace is running) and the warmer months we just run the ceiling fan (which helps to keep down the electric bill since we don't have to run the A/C as much). As long as I don't have an action movie cranked up when my wife goes to bed and I keep the volume at a reasonable level, she doesn't complain really at all. Having the white-noise on also helps me sleep better as well, since any noise from cars, trains, neighbors, cats, dogs, etc. will be drowned out. This option doesn't really cost anything.

What I just mentioned may not be a solution, but may work well in addition to some more inexpensive things that you can do in the home theater to help isolate the sound from the rest of the house.