since the the RCA is just an analog signal there is no power to "drive" your headphones, and hence no control of the volume.
Does your TV have a headphone port on it? I assume no since you are using the RCA but I just have to ask.
If no headphone port, powered head phones would definitely work. They 360 specific ones from
Gaming Headsets USB PCI Sound Cards - Turtle Beach which I have seen get favorable reviews. They also have an integrated mic which is nice.
EDIT: Welcome to Head-Fi, and sorry about your wallet