I want to pick up a vintage SS integrated

For a stop-gap measure, you could pick up a new Emotiva A-100 for $230.  This amp will out-perform the vintage amps you are looking at and will come with a three year warranty.  You may well decide to give up your search for a restored vintage amp, but at least it will buy you time while you are searching for a reasonable deal or messing around with finding parts, new caps and pots, and cleaning and refurbishing an old unit.

Nitewulf:  If it's aesthetics you are after, I cannot help you.  That will be a personal journey.  But I get it.  I thoroughly enjoy dragging out my ST-70 and PAS 3x and hooking them up to some ancient Altec horns.  I have a 100+ year old old oak cabinet Silvertone windup that is a blast to listen to old '78s.  Those early '70s Japanese ss amps have a cool vintage vibe, and recapped and "hot-rodded" can sound pretty decent.  But sound wise, they are bettered by modern well-designed amp from a reputable manufacturer.  There have been many advances in electronics design and manufacturing that are available to modern designers and engineers that enables them to produce high quality gear at very reasonable prices.  The legendary designers of days past did marvelous things with the materials and equipment available to them, but it is disingenuous to think that modern engineers are not "real" and that they all pander to a rarified audience of wealthy patrons.

Please go out and enjoy your vintage journey.  If you are the soldering iron type, it could be very rewarding.  But if I were you, I would consider just going out and buying the Luxman and be done with it.

In some ways build quality was better, in other ways not.  The chassis and casework is usually heavier gauge, fewer ICs and more discreet wiring.  Pots and connectors were chassis mounted.  Nice wooden cases.  But the components were built to lower tolerances and are not as well matched, and some of the technology available in new amps hadn't been invented yet.

I'm guessing the KA 5700 cost about $350 back in the day.  That would be around $2500 today.  For that money, you could buy a brand new Yamaha A-S1100 (complete with VU meters) that would certainly out-perform it and have probably better build quality.  I'm guessing the Yamaha would give the Luxman a run for its money (of course it all depends on your speakers, room. power supply, etc.).

I can understand how a vintage piece in good working order (new caps, etc.) would be a reasonable "stop-gap" option (if you can find one at your price point).  It could also be an interesting DIY project, if you are so inclined.

My gear is not very glamorous.  Being of modest means, I selected for sound quality over aesthetics.  But inside those plain looking steel cases are some excellent electronics.  My speakers look pathetic, but they sound good.  The turntable I am currently using is certainly not styled to my taste, but it works well.  Nobody is impressed when they look at my system.

I certainly would not be satisfied with a $225 Emotiva amp.  My stuff is considerably more expensive. It suits my needs.  However, I doubt that insanely expensive stuff sounds much better than what I have.  At a certain point the law of diminishing returns kicks in.  It's like my $250 watch.  Stainless case, Swiss mechanical movement, Sapphire crystal.  I doubt that a $10,000 Rolex keeps better time.  But I wouldn't mind having one!

Yes, the legendary showman Bob Carver and his studly Flame Linear 700s.  Now those suckers had some meters on 'em.  Pro Audio handles.  Ungodly amounts of power.  Fry an egg on 'em.

There was something remarkable about the stereo culture of the late '60s/early '70s.  Before that, stereos were nicely tucked away in mahogany console cabinets.  Mom would play Tijuana Brass and Christmas records on them.  Then along came rock 'n roll and an entitled generation of baby-boomers.  Stereos went from polite furniture to raging expressions of male hormones.  Girls were scared of them.  That Zenith console (which probably had a tube amp) gave way to big-balled ss amps and 12" Utah speakers in giant plywood cabinets.  The rich kids were doing Macs and Klipschorns.  Those were the days, when you wouldn't measure a man by the size of his house or the cost of his car, but by how loud his stereo could go.

My girlfriend had one of those KLH compact systems.  Nothing like a crock-pot full of lentil soup, a cafeteria tray full of weed, and a stack of records on the turntable - rocking out to "Spanish Moon".