Tuner or Receiver

I'll preface my main point and question by saying that I recently bought a used Yamaha RX 596 Receiver which is around 15 years old.  After biwiring my Castle Conway 3 Towers to it, I have been blown away by the sound from this system.  Far better than any previous amp I've used with these speakers and probably due to the 85 wpc vs 60 wpc or less and only using a single speaker cable for each.  


This leads me to the question about tuners and receivers.  Currently I have a Carver TX11a and also a Onkyo T-4310r.  Both are quite old but still work fine.  But...  Has recent tuner technology advanced beyond the the units from the 80's and 90's?  Is the sensitivity of the AM and FM sections superior these days and is the selectivity also better?  I don't need Digital FM and still listen to analog AM and FM.  Just want to know if I would be better off with a new tuner or receiver that would offer better audio quality or better signal capturing ability?  The tuner in the RX 596 is OK but also dates to about the same time as the Onkyo tuner.  Onkyo seems better too.