Stay away from the nad

As per PSB Specifications It's 6 Ohms nominal, 4 Ohms minimum.
You actually posted Specs. for the Synchrony One but towers. They dip down to 2.6 Ohms.

djengan-

I always wanted to demo Accuphase gear. Whom is your dealer/retailer?

Happy Listening!

Maybe use a credit card,so you get an extended warranty.Most credit cards add 1 year to manufacturer's warranty and some add 2 years.So,you could have had a 3 year warranty.Maybe next time.$400 is crazy for that repair.I would say about $75 max.That's what I would charge and still make good profit.

I've found NAD to be Not Always Dependable. My T758 was bought as a refurbished, and 6 months out of warranty the DSP portion of the AM100 module failed. Thankfully my dealer had a used trade-in AM100 from a customer who updated to a newer version, and I got it a lot cheaper than the $400 price of a new one. To put $400 into a 1-1/2 year old $700 receiver would be a non-starter for me. I don't really trust this unit, but I'm stuck with it for a while.

I purchased a 3020 NAD in 1979.  It has moved across the country several times, lost a button,  has a cracked faceplate and sits in my garage -- it works flawlessly.  It has never failed.   It is regretful if newer NAD equipment has problems.