Interesting thread with all manner of fascinating responses:
1980 Acoustat Monitor 4
1985 Apogee Full Range with AR D-250 Mk II amps - Saved on heating bill
1991 Goldmund Dialogues with Janis woofers - these actually are marvelous with SETs.
2001 Acoustat Monitor 4 to present updated some years ago by Joe Curcio. The amps actually are sneaky wonderful being OTLs and driving the panels full range. With all tube circuits, bass is excellent with completely flat frequency response. There is still only one sweet spot for imaging and depth. Office system since the 90's Quad 57's updated by QS&D with amplification by vintage LA Audio SETs running 2 300's per side.