Outstanding sound quality, plus the unique SDA effect.
See if the interconnect cable is a blade/blade or pin/blade. I think the original SRS was blade/blade. They're worth less than the 1.2 or 1.2TL. Maybe $1200-1500 if absolutely perfect.
Great speakers and if fed with a nice big amp will be very enjoyable!
Only if you are bridging a pair of amps. Otherwise, you don't need it.