The trouble is, most reviewers say everything is great and if they do talk about differences its things like air, PRaT, warmth, smoothness, etc. which in the case of cables, amps and DACs, likely don't really exist anyway. If they do attempt to put things in order of preference, it's almost invariably pretty much in price order, whereas objective testing by Amir and others has shown that price often has very little correlation with measured performance.
I thought Crinacle's video on the subject of useless reviews was quite good: