Most reviews of the AK 120 MkII state that it sounds the same as the AK240 .
I've moved from AK120 MkII to AK320 and it sounds better - more detail, more air, better soundstage (AK 120 MkII is warmer but also sounds veiled now I've upgraded).
So by logic, the AK320 must therefore be better than the AK240. I've not heard the AK240 myself but all those pro reviews can't all be wrong?
EDIT : Sorry, I just realised that that was your opinion based on audition. I can't argue with that at all, and for you the list is correct.
But logic says that others must disagree.
I auditioned the original AK100 against the AK120– the difference being 1 DAC vs 2 DACs (1 per channel). The difference was a huge jump. The AK240 was a smaller upgrade over the AK120, and the jump to the AK380 was not worth the price or size increase. The SP1000 is very nice- but I haven’t A-B’d it directly with the other models. It’s the form factor that keeps me with the AK240. It’s a perfect size.
But if you’re REALLY interested in upping the sound quality, adding a Hugo2 to the chain and using the USB out of the AK will yield a greater sound improvement than changing any AK for a newer model.