I think I understand what Spidey is trying to achieve - a 7.1 setup but he has only 5.1 speakers at the moment. I too have done this and worked well while I had it that way. My requirement was that everything is in the same room, front speakers are shared between stereo listening and movie\multichannel audio. I am assuming Spidey also wants to do the same. BTW, I have now seperated both, though they are all in the same room.
Here is how the connections would need to be:
2 Channel Source -> Emotiva USP-1 stereo pre -> Emotiva 2 ch XPA-2 -> Front Speakers
So far, same as any Stereo System (Stereo quality does not suffer as there is nothing additional in the chain)
Here are the changes if you want to make it work as per your requirement:
- Left and Right Channel RCA out of Emotiva UMC-1 av processor -> AUX(or any free source input) of your Emotiva USP-1 stereo pre)
- Remaining RCA outs (you should have five plus one LFE remaining as UMC-1 is 7.1 to the inputs in your UPA-5 amp
- Connect Speaker outs from UPA-5 amp to centre and two surrounds. You will have two channels not being used because you have seven channels and 5 speakers. Buy another pair of surrounds as and when required.
- Connect LFE out from UMC-1 to sub
For, listening to music in 2 Channel, turn off the UMC-1 and 5ch UPA-5.
For watching a movie keep all equipment on, select aux as input on the input selector in your USP-1, turn on bypass mode (this will cut off the volume control on your USP-1 stereo pre so you can control the overall volume using the UMC-1. This way you will not have to do any wiring changes when you have to switch between movie and stereo mode.