I've just read John C's reason for changing to a Tyros 3 because a)you can use USB sticks and b) it does have a small on-board hard drive. I agree with most of what John says with the exception of No.2 - "easy to operate" ???
In my opinion, the Tyros keyboard's Operating System hasn't changed much over the years with the exception of the Tyros 4 which now offers an expensive optional extra but I think it is still unnecessarily complicated in that it uses different areas for saving i.e: Voices, Styles, Registrations etc. and almost every single move has to be saved in the correct area or you lose your set, or worse still, it cannot be called up because it has been saved in the wrong place. You have to go to the area button first before accessing the actual area. You also have to be very careful when changing parts/icon or renaming your set, as this could 'break the link' thus causing further complications.(can you believe that?) There is an awful lot of button pushing involved with this keyboard which is also very time consuming.
With Technics once you have saved your set, it can be called up by Folder, File, Numerical or Alphabetical accessed immediately via the load button. The KN7000 uses an SD Card which makes it even easier to save and call up your tunes but, you can only save 99 Folders to an SD Card (more than enough for most people). However, it doesn' have the facility to save to a USB stick BUT depending on the model you have, you can add an internal hard drive if you wish.
1) Yamaha Tyros 3 would be a good choice as there are numerous converted Technics styles available on the net that it will quite happily play. The USB stick is quicker than a Floppy Disk but for me, it isn't as quick to load as the SD Card.(or as reliable)
2) Technics KN7000 is also a good choice as the SD Card is quick to load and has never failed when calling up saved Folders/Files/Songs, making it definitely easier to operate.
You have to remember that while the KN7000 keyboard is still among the top keyboards, the sound system isn't as good as the modern keyboards but I play mine through an amplification system and you can barely tell the difference. However, each day it is getting older which will obviously reflect in any future part-exchange price plus of course, the ordinary SD Card is becoming harder to find in the shops. An SHDC Card will not work - these are for camera's only.
Hope this helps.