Some receivers do a better job at allowing more than one thing to be done post processing. My last Pioneer allowed me to use Automatic Leveling Control OR PLIIx at the same time...not both. My new one allows me to use Neo:X, Audyssey room correction, AND auto leveling control at the same time. This allows the receiver to do a better job at making me happy since it sounds better.
Oh - I must have misunderstood you. Above you're saying DSPs etc make a difference to the sound. Yes I agree.
But before you said it was better tolerances and better components such as resistors.
"The tighter tolerance does a better job, and cost more. Not all the internal components in a piece of audio equipment, or anything else for that matter, are created equal. Better stuff cost more. It does a better job. You pay for that. You also reap the rewards for that."