There are a number of people waiting on the 950 who currently use the 1050 with six speakers, but the ideal would be to go on up to seven and add a pair of surround back speakers on the rear wall (leaving the surrounds right where they are now, even with the sweet spot). Those speakers could be identical to your existing surrounds, but don't necessarily have to be. I read somewhere that THX has begun suggesting direct radiating speakers for the surround back (they still want dipoles for surrounds), but dipoles seem to work well in that role as well and I've heard some people prefer dipoles in surround back. I personally run a single surround back speaker, which is identical to my surrounds.
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Gonk