There are VERY FEW avr/preamps on the market that will truly pass analog audio through their hardware without changing it to some degree... even when the OEM claims that it doesn't.
It's quite possible that even in the proper setup/configuration, you may not be able to discern the difference in audio quality that the BDP-105 offers,but that also doesn't mean it doesn't exist.
All of the enthusiasts and professionals who have heard the difference can't all be wrong.
Sometimes it's better to listen to what people have to say when they know the facts from years of experience, rather than to come up with guesses and theories.
There are a lot of very knowledgeable people here willing to help if they can, but you you have to be willing to listen in order to gain anything from it.
As Spock once said...
"...if you eliminate the impossible, whatever remains , however improbable, must be the truth"