I have an iPad and a Casio cdp s100

What’s the cheapest route for me to take to get top class sounds ?

iPad apps ? How good is ravenscroft 275 ?

I already have Galileo organ and korg module - I even bought the ivory mobile grand IAP but it does not sound anything like it does in the demo they give u to listen to - I feel cheated - the grand piano sound on the Casio sounds far better and it’s a cheap entry level keyboard - the piano sounds on module itself are also rubbish - again I feel cheated - the demos sound great but then u buy it and it’s rubbish

Naturally I don’t want to buy more and more apps and be disappointed again

Should I get an older keyboard such as a tyros 1/korg pa1x or similar and connect it via usb midi to the Casio ?

The Casio has an audio in so I can take the sound from another board that way but I would prefer to have just one keyboard

Should I just go the whole hog and get a better keyboard ?

If I sold the Casio i could afford to buy

Korg grandstage/Kronos 1
Roland rd800/rd88/fp60
Yamaha cp73/p515
Nord electro 5d/piano 3
Kawai mp7se/es8
Dexibell p7

Which of those keyboards has the best range of great sounds ?

I like built-in speakers but don’t mind having to get headphones if that means better sounds

Not bothered about key feel/action as the Casio feels fine to me so am guessing all those other boards will feel better

Looking for the best range of sounds I can get especially synth and electric piano - I thought buying apps would be the cheapest way to do it but it hasn’t worked out that way

I want to get a wide range of great sounds