It’s Obvious, QVX.
Well, umm… The Casio WK-7500 is a must have for every entertainer who doesn’t have to spend too much money to buy a professional keyboard, but i guess you should look for a Yamaha PSR-S750 or a Yamaha PSR-S950 instead if you could spend more money.
Casio made 3 new keyboards: Casio CTK-6250,Casio LK-127 & Casio LK-247, they are fine keyboards to mess around with, but i would go for a Yamaha PSR-E433 to start your piano lessons.
The Yamaha PSR-S650 seems to have less features than the Yamaha PSR-S750 or Yamaha PSR-S950, but it seems to have a newer LCDisplay.
Yamaha especially released a special Oriental keyboard called the Yamaha PSR-A2000, an Oriental keyboard to mess around with because of the Oriental instruments.
The Casio Privia PX-5S is a digital piano with some Blue on it.
Lets go back to 1990, when the next Yamaha’s got released: Yamaha SY-22,Yamaha PSR-2,Yamaha PSR-3,Yamaha PSS-50,Yamaha PSR-4600,Yamaha PSR-8 & Yamaha PSS-190.
1 year later, the Yamaha PSR-18 was released.
The Yamaha PSR-19 has the same case & buttons as the Yamaha PSR-18, but with other color scheme & the buttons from the voice presets seem more professional.
Another favorite is the Yamaha PSR-4500, it’s a nice high end keyboard to mess around with. Ando Umeda (from YouTube) owns this great keyboard, besides this, he even owns: Solton MS-20,Technics SX-KN3000 & Yamaha PS-6100 for example. (you should go to youtube & search: Yamaha PSR-4500 demo)