Casio CDP 120 is having maximum 48 polyphony. Is it enough to play the HARDEST AND COMPLICATED piece ever composed?
Anyone capable of playing the hardest, most complicated pieces of music is unlikely to be overwhelmed by the CDP-120, for reasons having nothing to do with polyphony.
What actually is polyphony? What I know is its the number of voices you can play at once. But does it include the pedaled notes? Say if we are playing 48 notes with the pedal the 49th note cant be played?
In addition to reading that thread mentioned above, to answer your specific questions, yes, polyphony includes pedaled notes. In fact, if you're playing a stereo sound, you typically use up 2 notes of polyphony for every key you play (including pedaled ones). So on the Casio, you would not hear the 49th note on a mono sound, or probably the 25th on a stereo one.
> What i am looking for?
a) The acoustic piano feel, weight and sound.
If you want the closest thing to "acoustic piano feel, weight and sound," you could look at something like the Yamaha AvantGrand, which start at $5k+ (and go to about triple that). Short of that, you should always expect compromises. The acoustic feel/weight/sound is what we all want, and if any cheap boards truly had it, some of the most expensive boards wouldn't exist. ;-)
After playing in my digital piano i should not feel any difference when i play in an acoustic piano. (like width of keys, weight etc.)
Keep in mind that you can also feel a difference switching from one acoustic
piano to another. But if you at least want to choose from models that feel like some acoustic piano (though not necessarily any specific acoustic piano), I think you probably need to look more in the ~$2000+ range. Though some people are pretty content with the $1000 Yamaha models (P155, CP33). Below that, I don't think anyone finds anything to feel like an acoustic.
a) I dont need any of the keyboard features say number of tones, layering, chorus etc etc. I just need the piano tone.
If you're looking for something somewhat portable (i.e. not "furniture"), and want the best actions/sounds but as few non-piano features as possible, there is the Yamaha CP1, Roland V-Piano, and arguably the less expensive Kawai MP10. These companies also all offer cheaper models, which are not quite as good from a piano perspective (the hardest part to get right), but also have much more in the way of the features you don't
want. But if you could live with the fact that they threw in those other features, you can get somewhat close to the CP1 with the far less expensive CP5; and you can get a scaled down version of the V-Piano technology in the RD-700NX and FP-7F.
In low end models, the P155 probably comes closest to what you want. If even that is too much, personally I would take the Yamaha P95 out of the crop of low-end models (peoples' opinions differ there), but also, there are some new models coming out later in the year... the Yamaha P-105 (which is supposed to sound better than the P95) and Casio PX-150 (which is supposed to sound and also feel better than the previous Casios). If nothing else, it is pretty likely that that new Casio will be a big step up from the CDP-120 while still being a budget model (though not as cheap as the 120).