The 1970's Infinity QLS 1...How would it compare?

How would a properly driven (worth a 500 page thesis in itself!) pair of these compare to $20,000 and under mainstays of today? These speakers have become an enigma to me...They were always two or three or a hundred and fifty steps beyond my grasp for different reasons and now they're getting hard to find and harder to find parts for so as to be forever relegated to the "one that got away" files. Anyone ever own these or otherwise spend any time with them? Closest I ever got to auditioning them was prob. late '78 at a Pacific Stereo (Unfortunately someone had underpowered them with one of the 80 lb. "monster recievers" of the day only hours before I got there so all I got was a look.) Ah, youth........