What’s the most underrated used Audio Research gear?

I've been using an ARC LS7 that I bought used back in 1998(!) and it has consistently been an absolute champ. I have turned it off a handful of times in that period, and never changed a tube. what a demon!

I will back the Classic 60 Amp also.

Have owned mine since New, and it has been Rebuilt and Modified by Scott Frankland and Associates. He installed Bias Pots on the Back Deck & Test Probe Ports on the Side in proximity to the Bias Pots. Absolutely brilliant since all I need is my milli amp Tester (Voltmeter) with Probes and Adjust, and or Check the Bias Monthly.

Scott has also Replaced all Caps and the Amp works flawlessly.

In the time that I have owned this Amp since New, I had one Failure a number of Years ago when I tried KT90 Tubes. One Tube blew the Grid Resistor and it also took out a FET.

Recommended Tube now, even by Audio Research, is the Sovtek 6550WE which is the only type that I use. KT90 Tube experience was not pleasant. 

Months ago, I started researching:" What Amp would I replace the Classic 60 with if needed? " After many Months' reading everything I can get my hands on which includes this Forum, I do not have a Clue.

+1 @jimmy2615 

Have the 100.2. Was recommended by Marc Mickelson, a reviewer with Soundstage at the time I bought his ARC Ref3 and PH-7 through Agon (now with Audio Beat).  Love it. Has very limited negative feedback. Unfortunately I think it is now on the list of ARC gear they will not repair as some resistor is no longer available. Regret having sold my Ref3.  Warm musical darker sound signature. Currently looking for used ARC preamp, likely 5SE, but appreciate this thread and input above.