I did find AVRs and amps from years ago sound more different from one another than they are today. Even now I believe it is still the case for entry level gear. Once you get pass the HK1XX, Denon 1XXX, Yamah RX-VXXX, Onkyo 6XX, Marantz 6XXX level you are going to have hard time telling the difference unless your room and speakers demand more power than those AVRs can handle at ease. That is why it is always good to go with AVRs that offer preouts, for future growth.
If you are sensitive to minute difference in sound, that's good for you but for most people, as long as they have enough power for their system/room they should go with the features they need, reliability track records, and the look they like etc. If they need more power than they could add an external power amp and be done with it.
For gifted people like you who has the ability to hear the minute differences, the particular "difference" that you like may not be preferred by others. I prefer my system to sound like what I hear in live concerts. You can call it "bright", "warm", "dark" or whatever but as long as it sounds like "live", I am happy but that's just me.