Do I really need a newer Reciever ?

I don't understand completely the newer home theater recievers out there. The newer good ones have processers that can decode signals from a regular dvd player and upconvert it to high definition and send that signal to your TV through the HDMI cable correct?
What about BlueRay where does that fit into the equation?
What if I have a blue ray player already? can I just use an older reciever by sending the picture to the TV through HDMI cable and then using the analog rca's to the reciever for sound?
If your BluRay player can decode Dolby True-HD and DTS-HD Master, the analog outputs can go right into your older receiver.

The advantage of a newer receiver is that HDMI simplifies everything to the point of using a single cable for video and (up to) 7.1 of Audio.

This is very helpful if you have more than one HDMI device (I have three).
I faced the same choice a few months ago. Most all of the newest receivers all have HDMI connectivity and one cable per component for all audio and video inputs is so much simpler. If your BlueRay player can decode,then as Dweller mentioned, you can use your old receiver, but the cabling can be extensive should you want 5-7.1. I have a big old drawer full of audio and video cables that became useless once I made the change. While I haven't experimented with many different HDMI cables, the consensus of professional and amateur opinion seems to lean towards the issue that
high priced HDMI cables don't really work any better than reasonably priced ones. Besides, there are plenty of inexpensive home theater receivers available that are much, much better than the rediculouly priced receivers of a few years ago.