Would it be complete sacrilege to get the 009 but "only" the SRM-252S amp?
I prefer solid-state to tubes, so that rules out most compatible higher-end amps. The 323S is probably what I'd otherwise get, but its depth won't physically fit well into my setup.
I'm sure there are differences, but are they likely to be audible to an audiophile-voodoo skeptic? Would the difference be likely to pass a proper ABX test, regardless of what you think of the value of ABX tests?
I have compared the 323 to kgsshv with sr009. It is definitely audible to novice. Never tried 252s but if you think 323s is probably better, then yes you would hear a difference. I used the kgsshv as example as it is solid state tube. Sr009 is arguably the best headphone out there. However it is easier to get a decent sound out of it than the sr007, IMO, but it scales as well. Personal opinion as to whether or not this means you can cheat on the amp. I would look at kgss or kgsshv if i were you. I think there is a compact build of the kgsshv someone is making.