While we're at it, I see lots of SA-7700 integrated amps, and usually paired with TX-6700 tuners. It appears to me that the TX-7700, while it was actually produced, is quite rare. I have never seen one come up. I think that one of the reasons, was that the TX-7700 only has 1 meter, while the TX-6700 has 2 meters, to match the VU meters of the SA-7700 better. Maybe that is why most folks bought the TX-6700.
By the way, I just did my 1st reveneer and finish of an SA-7700/TX-6700 combo. They originally came with that oh-so-fragile fake wood vinyl that tears and peels, for apparently no reason. I took all that off , and replaced it with real walnut veneer and finished it with Minwax stain and polyurethane (antique walnut). The match is almost perfect to all the other Pioneer walnut cabinettes I have, and it even matches the original look of the vinyl it replaced (I have more of these units to compare to).
Rich P