I'm not sure what you are trying to say about switching on a cabinet. Do you mean that you want to watch TV on your monitor without turning on your computer?
If so, that's not going to happen since any PC tuner card will need the computer on. You would have to have a monitor/TV with a built in tuner.
If you really do want your computer on and are looking for the best external TV tuner, then the answer is the ethernet based SiliconDust HDHomrun.