This was also when (1983-1997) HEA had it’s biggest and most actively productive membership. I was so disappointed when the quest for $$$$ became the driving force instead of the sound that so many of these companies provided. The basic models sounded much better than the over built ones and the designers knew it, but the pressure was on to get the gravy train in full gear.

Fortunately the mass produced companies picked up where these basic audiophile products left off.

Michael Green

www.michaelgreenaudio.net

Oh, I should probably add this for a point of reference. During these years I had my own HEA stores. I spent a ton of money trying to get the most out of the pricy products, but started to feel guilty selling them when I knew the basic models were able to out perform them. Same thing happened as I was doing trade shows. Because I was providing a popular acoustical product the high enders wanted me to do their products in my own rooms, but again it was a conflict for me.

Not sure if the OP is asking for opinions or recommendations but either way the 535 was actually a better amp as compared to some of the higher power models like 545 or even 555. It is also more easily and cheaply upgradable. I've owned all three models (still own 555) and for moderate listening levels the 535 has a fuller and cleaner sound than the 545/555. 
Sorry gentlemen,but Thresholds were better in the day.
compared both many times back then and always picked the Lwr pwr ones for better overall sonics and build qualities.

Nelson pass is still a “Benchmark” for solid business practices and customer service,unlike some of the questionable companies of today that just come and go and don’t stay in business long term.

Happy Listening,
Kenny.
Back when Adcom was buying a lot of full page ads, I had the opportunity to use one for two weeks in my system alternating with my Mac 2105, which was pretty old even then. I can't recall which model, but it was well over 100 watts per channel. Anyway, the sound was thin, hashy in the treble, and overall not even comparable to the Mac. It still makes me wonder where all of the praise is coming from. At the time when they were popular, they were well priced amps for people who couldn't afford a higher end, higher powered amp.