As for 6.1/7.1, the only processing I am aware of that produced true 7.1 ("stereo" surround back channels) is Lexicon's Logic 7. Dolby EX, DTS ES, Cirrus Extra Surround, and the rest send the same signal to both surround back channels, exactly as you have read.

The 1050's amp channels are dedicated -- there is no way to re-assign a channel. That feature does still show up in some receivers (I think some of Denon's higher-end receivers can do this, as well as a few other brands), but as far as I know it's pretty much unheard of these days in the 1050's price range.

If you do wire the two speakers in parallel to the center surround amp channel on the 1050, then you will need to switch the 1050 to 4 ohms (per page 23 of the manual). As far as I know, this would have no negative impact on the other speakers. The 1050 runs pretty darn warm. I would definitely not set anything (including a Model 200) directly on top of it.

Wiring the surround back speakers out of phase is a new one on me -- can't help you there. Sorry.

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