Maybe not sleeper, but I always thought the “SE” versions of stock ARC components were meaningful (but pricey) upgrades and when bought used you get the upgraded versions at a very nice discount. Kinda like when you buy used SMcAudio-upgraded McCormack amps — quite the bargain I think.
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.