Gotcha, thanks. Which Sony system do you have?
Ideally, you'd have a system that could take advantage of the surround sound audio from DVD, digital TV, and blu-ray. To do that, you'll need either multi-channel analog inputs or a digital audio input. Does your system have either of those?
If you don't want to buy any new equipment, I don't think that you can accomplish everything that you want. Namely, only having one set of cables running to the TV while still getting audio and video from all of your sources on that receiver. You can get audio/video switchers, but that's different than a component video switch (very similar, but with additional jacks that are switched).
If it were me, I'd do this (and this is just an idea for you) - get a new receiver that can handle HDMI and video conversion from component video to HDMI, and run a single HDMI cable to the TV. With that, you can run component video from your sources to the receiver, run HDMI from sources to the receiver, and run a single HDMI cable from the receiver to the TV. That would require a new receiver, though, so just a comment.