The SP9 II & III were very good preamps that don't get mentioned often enough. Also the SP6 was great piece.
What’s the most underrated used Audio Research gear?
Sure, everyone loves the SP-8, SP-10, etc., but what about the sleeper ARC gear that’s still a good deal used? Recently got a used SP-17 and love everything about it for the price, but it got no love from either the press or the boards.