opinions

I don't think there is too much to think about...they probably are both good for the job. I personally would probably go for the NAD, but its not a huge decision.

Have your AR's been restored...foam surrounds and caps? You want to get the most out of them and make them easier to drive. The AR is not an efficient speaker.

The NAD is an efficient amp and puts out more power than its rated 30 wpc and may be able to drive the 10" woofers w/o any difficulty.
The Sansui 666 is from the 70s and would make for a nice vintage system. If at all possible, try and audition the Sansui with your speakers.

How large is your room?

Was the Sansui built by Luie Cifer...?!

Which NAD 3020? The classic vintage one or the new Hybrid Digital?

I think its safe to say its the old version for a few reasons. 1. Its been serviced. 2. He's comparing it to a different vintage amp that has been serviced, as well. 3. There really isn't 2 versions of the amp. 3020 is the vintage NAD, and D3020 is the new digital amp. Different model numbers.

yes my speakers have been restored and my room is an average sized living room

Oops Zd, I was thinking D3020. Vintage makes sense.

Sansui-loud, hard, fatiguing. NAD-high volume, neutral, warm, non piercing.

Sorry Matt, not this series of Sansui, the later ones, yes. Some even describe this series as a "tube-like' sound. I have heard receivers from this era, and they do sound good. As far as choice, Sansui offers more features and more power (35w vs 20w). Both should good, but maybe a little different.

I'm just curious as to why the vintage gear? I've done some experimenting with vintage pieces myself, and the only type of components I thought worth buying were tube amps. Didn't care for anything solid state or even tube preamps. To be fair, I haven't heard the NAD in a very long time, and never heard the Sansui, but I don't see why they would very different than similar products I did listen to.

The Sansui AU series is highly regarded for its sonics and build quality. They are not completely neutral sounding, more pleasant sounding than explicit, but they do provide long-term musical satisfaction when matched with sympathetic loudspeakers. I use an AU-999 with EPI 202s and I suspect your ARs will be a good match. I've never used the phono input so I can't comment.

I owned the Sansui AU-555 back 70’s and agree with Tls49 and Onhwy61. That said, I would buy something much newer as suggested in your other thread. Never mind my question concerning the AR2s there. Enjoy!