Doesn't that almost imply that all amps sound the same? And if so, other than current delivery/power and slight tonal differences, why bother upgrading amplification?To my mind amplifiers amplify, detail retrieval is the job of the source.
If anyone fancies a test get yourself a cheap Cambridge A1 from eBay and compare it to your usual amp with same source. A1 does a fine job but will miss a lot of nuance. I was shocked when I briefly had it how it performed (it's actually quiet enjoyable, but hi-fi it ain't).