Agree with Pete's assessment of this. And why worry about the modern equivalent to an AU-919 when the real thing can still be readily purchased (yes, somewhat costly, I know) and can be restored for many years of further enjoyment. Besides, overall build quality will still probably be better than all but the most esoteric, obscenely expensive amps presently in production.
Anyone with big money to spend can buy a brand new amp, but something like a 919 is more of an heirloom as I see it, and worth putting the work and expense into a restoration to have something truly special, rather than the newest, shiny obsession.
Obviously, as a big fan of vintage audio I'm biased, and I'll readily admit that. But, I look at this old gear as something exceptional, as it was the culmination of numerous factors - economic, technological, heck, even social in some respects - such that we will never see the likes of again. Very much a product of it's time, and in a good way.
For me it goes beyond just listening. It is part nostalgia, but also a deep respect for the achievements of the companies - and the individuals working for them who contributed exceptional skill and talent to design and execution of this gear - that inculates the ongoing fascination with vintage audio equipment. Some may think that is an odd way to think of big metal boxes full of electronics, but it works for me.