what's the point?

What's the point indeed. The blind test tells all. As someone who has taken two blind tests it was a subject that interested me, so I looked for all the blind tests I could find and the only one that ever showed a hint of a possible difference in amps was John Atkinson's (of Stereophile), who said there was a "slight" difference between amps. And he admitted there was a measured frequency response difference between the two amps and that the difference heard could be the interaction with the particular speakers used. He seemed to be fair in his analysis that given the small difference between those who could tell the difference and those who couldn't, along with a myriad of other explanations (and excuses), he didn't come down with a hard-core "Yes" or "No" answer, but one with a ton of caveats and leaning toward the suspicion that only a few highly trained people could "really" hear a difference.

You can read the whole test for yourself.
https://www.stereophile.com/features/113/index.html

And just in case you missed the Stereo Review article that stirred this whole subject into a firestorm, here it is.
https://web.archive.org/web/20060313071857/http://bruce.coppola.name/audio/Amp_Sound.pdf

though Julian H did say he would choose the Mark Levinson of all the amps he reviewed...(I forget which model it was)...

If a blind test has negative results it doesn’t mean anything. There are simply too many things that can go wrong. Besides, conclusions are reliable only after many tests have been performed, both for same system and tester as well as independent systems and testers. Repeatable and transferrable.

All my amps sound exactly alike with the volume off. 

There is no point in buying an expensive amp or an expensive anything for that matter. Buy what you can afford and components that take you to the experience you are looking for. Be reassured that amps etc. do make differences and nothing sounds the same. I have a good friend that debates this with me endlessly until we finally took the speakers out of his system and inserted them into mine. Of course my room is different, components etc. and so we tried our very slack A/B in the near field in both systems. Less than a minute, he couldn't believe it. Next my amp went to his system. Couple of minutes later he is trying to buy it from me. Not really a revelation. I do find the diminishing returns part of this interesting though. Of course how fat your wallet is the biggest factor but for me things start getting weird at about 10 k for amplification. I tend to look at the whole system and component synergy. This is where a crown amp suddenly for some inexplicable reason may work as strengths and weaknesses gel in your system.