Wondering if anyone here knows a lot about Sony AV receiver setup - specifically use of the HDMI inputs?

I recently purchased a Sony STR-DA3500ES receiver and BDP-S760 blue-ray player. The receiver has a host of RCA, digital coax, optical, etc. inputs, all associated with a specific a source. For example, I can connect a CD player to the RCA plugs labelled SA-CD/CD on the back of the receiver, and when I select the SA-CD/CD source by pressing the CD button on the remote, I can hear the CD. However, the HDMI inputs don't appear to be associated with specific sources though - they're just called HDMI 1,2,3,4. So I have connected the blu-ray player to HDMI 3 on the receiver via a single HDMI cable, and when I press the HDMI3 button on the receiver remote I get great sound and picture.

Now, there is also a setup menu option to assign different input signals to the various receiver sources, so I can go into this menu, select the BD source, press an Option button, select Input Assign, and then assign HDMI 3 as the input video signal. But there is no HDMI option for the input audio signal. So when I press BD on the remote, I get a great picture, but no sound.

Call me old fashioned, but I want to be able to watch a blu-ray movie by pressing BD on the remote. Isn't that what it's for? If I fill up the other HDMI inputs (with MY SKY HDi, a games console, etc.) is it up to me to remember which HDMI button to press to see and hear the right signal, instead of just selecting SAT for satellite TV, etc? Isn't HDMI the "preferred" connection type for BD and other high definition media? Surely Sony haven't designed a range of receivers where it expects you to connect a BD player, but you can't use the BD-named source unless using RCA cables?