Still have my 't' mod cube out in the garage. Debate continues on the subject of total rebuild and use as a sub amp for a DVC homebrew design.
Al might have used his with higher sensitivity speakers, but I had very good luck driving a pair of vintage Magnepan MG-1s. It was neck and neck as to which ran out of steam 1st, Maggies or cube.
This was a very impressive (to me) combination especially after I added my First Ever CD player... A Magnevox / Philips FD1001 an original 14 bit player sitting in the next room looking for a laser pickup.
The Phase Linear stuff, especially the 400 is landmark equipment.