Are dedicated circuits with isolated ground and hospital grade outlets beneficial towards removing background noise?
If sharing circuits causes overload, dedicated circuits are the usual remedy. They cannot block noise from other parts of the house because back at the service panel, everything is still connected together.
Isolated grounding (insulated grounding might be a better description) may help prevent computers in large commercial installations from crashing, but can also introduce more problems than it solves, especially if mixed with conventional grounding.
If home theater one day starts using electrodes that are stuck to a patient's skin, hospital grade outlets may become standard issue, although some people prefer them anyway for their increased mechanical reliability.
Noise may always be present if you put your ear right against the speaker. This can be considered normal and acceptable as long as it can't be heard from a few feet away. Note that the more efficient the speaker, the louder it plays everything including the noise floor.