Sending identical signals to unique tvs

Hi. So, I am planning on a pretty sweet AV system for my new house, which will be as follows:

HTPC
3D BD player
DVR
Security DVR

- All of which will go into an HDMI matrix and be routed to sources such as -

1080p 3dtv
1080p 3dtv
1080p tv
720p tv
720p tv

The only problem with this as is is that when I switch to a 1080p source on a 720p tv the source will downgrade to 720p until restarted, correct?

So, I was thinking that the best way to handle the 720p TVs and EDID would be to buy AV receivers such as
http://www.newegg.com/Product/Produc...82E16882115313
that would take 1080p 3d signals and send a 720p signal to the tv.

I was also hoping that those receivers would handle any audio inconsistencies in the tvs. I've heard that they have similar problems as the video with the audio, as in it may degrade to stereo if the tv can't handle 5.1. The receivers should be able to take 5.1 Dolby TrueHD and DTS-HD MA input, right?

So, do you folks think that is the best way to solve this problem?

Can a tv with stereo audio out even accept a 5.1 signal and only display 2 channels?

Also, is there a way on most modern devices to force the EDID to not change?