...I've come to the conclusion that the professional and definition series components are the best looking gear of the solid state golden era...
....The aesthetic design of these was simply phenomenal, and one less appreciated aspect of discussing Sansui's history is who was responsible for the design work. I assume it was done in house, and wish we had some kind of background on that part of the company and the staff that was responsible for it.
Whoever was doing the design work really had an eye for making visually pleasing and usable gear. I might argue the follow on series, the AU/TU-717 was quite an accomplishment in understated but good looking gear as well. It also bucked the trend of flashy, silver faced components that was prevalent at the time..

Indeed, the list of top 5 will be highly subjective, though I can predict we will likely see quite a few "votes" for the AU-111, AU-517/717, AU-9900/11000/20000, AU-919 and AU-X1. I'll be interested to see others choices that aren't necessarily either the most famous or most common models, either older or newer than the frequently cited ones I've just listed.
For example, I really like the earlier 70's models like the AU-555A, 666 and 888, as well as the AU-G99X from 1984-85. I haven't given much thought to my own top 5 list just yet, but some of those could easily make the cut. I do have an AU-111, AU-101, AU-555A, AU-9900A, AU-710, two AU-919, A-80 and an AU-G99X here. Which covers a lot of the highlights from 1967-85.
...but my expectation going in was that he'd go in for the big dogs...
That's going to put the cat amongst the pigeons...
AU-505/999 are overrated
I would post 5 different alpha 907 models, and fill the list only with them but...lets do it another way.
1. Every Alpha 907
2. AU-X1 / AU-919
3. Every Alpha 707
4. AU-9500
5. Rest
Seems to me the 9500 is the single most divisive integrated amp Sansui made. Not having heard one myself, I can't make a statement on it either pro or con, but based on much reading of discussion here and elsewhere over some years, it is an amp that is either loved or hated. That leaves me struggling to understand what is so different about it's sound to cause so much debate.