The extra set of speakers terminals are for the difference between Movie Surround modes and Surround Music modes. Then you can toggle between the movie set of speakers and the music set of speakers. You can't play both sets at the same time, nor can you use the extra set for 2nd zone. There are a few receivers that will do simulated 9 channels, but they are big bucks (Carver is 1 I believe).
There is probably less difference between the 2807, 3806, and the VSX-82, VSX-84 than one would think. Denon uses Audyssey for their in room Auto-EQ. Pioneers MCACC was better than Denon's (in my opinion), but the new Auto-EQ might have put the Denon ahead. The newer model of Elites have switched from MOS-fet amplification to a traditional push-pull, so the sound of the receivers may be closer than with the older Pioneer Elite.
Unfortunately in the audio/video world, as in the computer world, everything is obsolete almost as soon as it hits the shelf. You can buy receivers that claim to be "future-proof" but they cost.
You probably won't go wrong with any of the big receiver names, Denon, Yamaha, Pioneer Elite, Maybe even Onkyo, or Sony. Second Act still has that Jamo receiver, that may be worth a look. You are wise to make sure there are enough inputs to handle your current and planned future equipment.
Have fun shopping and listening
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