Vintage integrated amp vs newer?

I have a collection of higher end vintage receivers and integrated amps. Several have been completely restored by expert techs. 

2 of my best that are restored are:
Marantz Esotec PM-6. 120 watts per Chanel with a 30 watt switchable class A. Full dual mono and higher end components inside. 

Sansui 9090db 110 watts per side. 

What is the difference between these and say a $3000 to $4000 new or newer receiver integrated amp. 

I would hazard a guess that my 2 units would keep up to anything newer in that 3k to 4k price range. 
People are always using the $ inflationary test for value. That's not what I am looking for. Forget the money. Just comment on sound and component quality. 

Any tech experts with opinions on this. 

Thanks