Yes, that is an old school way of thinking.
Is there a difference in any of the higher end manufacturers, Marantz, Rotel, Denon, NAD etc. at the $300-$500 mark?
The price is the big difference
Isn't it all digital and if you are hearing it then its is working?
Yes, it is all digital, indeed. But, something could be broken and still hear something
Can you get better then 24-bit, 192-kHz resolution in the $300-$500 range?
There is absolutely no need for such specs

You cannot hear it.
Can you get into the SACD- HDCD machines for under a $1000 whats the difference?
Thx
Don
Doesn't your HD DVD player capable of those? Some $200 DVD players are