What’s the most underrated used Audio Research gear?

I agree with Roxy.  Although the 100.2 was probably not underrated (try to find anything bad said about it, it’s all raves…), for the price, especially used, it’s a fantastic amplifier.  ARC should do what other companies have been doing and come out with retro products, like the 100.2 or the LS2B.  Sell them for $5000 or less to fill in that gap in their product line, they would sell like hotcakes and get more people into the line.  

The SP9 II & III were very good preamps that don't get mentioned often enough. Also the SP6 was great piece.

+1 ozzy62 

SP6 was my long time favorite.

ARC D-79B and D79 were quite good.  ARC made a lot of underachiever tube amps.

100.2. Owned one and should have kept her. Wonderful amp.