my old Yamaha PSR-225 |
It seems the more 'luxurious' models in the Yamaha series start with a 4 or 3, and 2 is the basic models. The 4 and 3's seem to have 'touch sensitive' keys, and presumably 4 is the best but seem slightly 'deeper' in size than the 3 and 2 series (only by 4cm).
The current models, and some discontinued models can be seen here
Latest models of Yamaha portable digital keyboards
At the moment, adding some recent discontinued models, I am looking at
PSR-E423, PSR-E413, PSR-E403
and from the 3 series : PSR-E333, 323, 313, 303