I always say for the same price for the keyboard... is a matter of taste. Some will prefer Tyros, some KN7000, other SD1...
I think the best way is to listen all those keyboard in the same sound system and shut off the inboard sound. Because if you listen a PSR-2000/2100 in is onboard speaker and you compare to KN2600/KN7000 keybaord amp sound system is very different.
I think Technics made is keyboard for the "first impression" looking. It's a board with a "Boost" amp and speakers built in. I had before the KN6000, and if you put the volume at full range it as some little bit of distortion in some sound !
I chage for the PSR-2100 for those reason:
1. the price
2. To have new O/S and new style. The Technics styles are very good, but they have almost a to big background. The fill in don't have enough "Break" pause.
3. I always play with the style and Yamaha is better organized because you could know the kind of intro, ending you will have before pressing the Intro/Ending button.
4. The loading of the styles is really fast: 1 or 2 second compare to 20 - 25 sec. in the KN6000.
If my budget was higher I was buying the Tyros.
Just by the keyboard you will think it will be the best to your ear and have fun !