Unsound, I used (and still do) an ARC SP10II. It was revelatory in its hey day. I wasn't so wild about the matching D115II though. Phono stage is still pretty good. And if I ever find some mint SA 1's I'll buy them just for the nostalgia effect if nothing else. :-)
BTW, I'm assuming you are familiar with Thresholds 'optical bias' which was introduced after the initial production of the SA series. Did you find it added to the sound, quality wise? I never heard it but the feedback I got was that it sort of brighten them up a bit.