I can't help you on NOS choices-- but the use of tube dampers is strictly to taste. I'd imagine the SP16, given its base sound, benefits from dampers-- but you might prefer it otherwise. Better than the dampers provided by Audio Research are the dampers from Herbie's Audio Labs. Not only do they sound better, but they don't bond to the tube with use, so you can experiment with the dampers on and off. They're great on the tubes in my SP9 Mk III.
