Hope this information helps.. It appears that the AR7 Hi-Res was discontinued long before the downfall of AR, since the Wayback Timemachine only has the AR7 Hi-Res listed on some of their oldest archived pages, but not in the latter years (when the page was black).
I own a set of AR1, 2 sets of AR15, 2 sets of AR17, an AR2c, an AR4c, and an ARS300. I love all of them dearly.
I have a pair of AR7s I bought in the UK in 1971 or so. . . Pulled them out yesterday after my ESS AMT1a's once again dusted the foam skirts on the drivers. These speakers have (10 years ago) newer rubber type skirts on the drivers with original voice coils and finally sound really very good providing I have a good power amp hooked up. No receiver o/p or all-in-one unit will make these sound anything like their true capability.I am amazed at how well these work in today's digital compressed crap audio etc world - I love 'em.