A lot of the current craze for older (vintage) Japanese receivers seems to be a result of comparing one of those old heavy workhorses against one of the new flimsy lightweight examples. Looked at in that way there is no comparison.
As far as any of them against an Adcom GFA-545 there is no comparison. The Adcom flat stomps all over them in clarity, detail and transparency. As far as bass goes they are simply in two different ballparks. The Adcom has bass that approaches true high end quality and character. The vintage receivers merely have nice bass.
If you want to improve an Adcom to the point of being a contender there are a few things you can do.
1. Replace the resistors with Vishay's
2. Replace the capacitors with Infinicaps or Musicaps or any other high quality caps.
3. Replace the rectifiers in the power section with high speed diodes.
4. Increase the power supply capacitance.
5. Replace the input connectors.
Optional
Change the AC cord to an IEC connector.
You have no idea how good the basic design of an Adcom is until you've heard one with upgraded parts.