Hello KABINOPUS,
You're findings make a lot of sense to me and not only with Yamaha. I had the PSR3000 as well many years ago and recently I had the PSR-950 for a few months. The thing I agree most about is the unpleasant bass response of the PSR950. Furthermore it should be noted that the differences in basis sound quality and character between the PSR models over the last ten years has not changed or improved drastically imho. (PSR 910-950-97-975 ).
We are now led to believe that the SX-900 is vastly superior to for instance the PSR-975 but so far I have not heard or seen any demo to convince me. No doubt there will be a number of sound and style improvements but the quetion remains whether it justifies spending yet again hundreds and hudreds of dollars to get the latest. (of course the insertion of a touchscreen is a huge improvement on the new Yamahas no doubt about it). But there is no accounting for tastes. I have heard a few Tyros 4 owners remark that paying another 2000 dollars or more does not justify purchasing the Genos instead of the Tyros 4, which just goes to show.
As to myself I have opted for a drastic departure of my KORG addiction. For twenty years I have had Korg as my main keyboard at home , generally with a cheaper yamaha or ketron on top.
I have sold all of my keyboards and bought a secondhand KETRON SD7. For my purposes, singing with the idea of having a real band backing you up, it is a fantastic keyboard and I got it for a bargain price. The only downside is the service and reliability which with Ketron is not always up to par. Those in the USA are lucky to have the Ketron services and back up of AJ.
At present therefor I only have the KEtron SD7 but I am most seriously contemplating of buying a secondhand Korg PA50sd to sit on top of it. Although the PA50sd harks back to the sound and styles of the PA80 and PA1X and therefor lacks sounds and handling of the new generations I find that listening to my own old recordings the older Korgs had something that is missing in the current generations. Something that resembles the fullness of the Ketron, particularly with drums etc.
Just an example of a recording that I made in 2004 with the PA80 which happens to be 100% identical sonically to the PA50sd
https://app.box.com/s/yb7h6cngpc4ane17pdml2tadfqvmsp3sregards
John