I have bought a CASIO CDP-130 digital piano - unfortunately it has only 48 polyphony. I only love classical music and that´s what I want to play. Will it be enough for playing most classical pieces as piano solo?
Yes. A full-range arpeggio flourish with sustain pedal might run out of notes, but I don't think you'll find it a practical limitation.
Incidentally, be wary of polyphony numbers on electric keyboards. 48-polyphony might mean only 24 notes if a layered sound - piano/strings maybe - is selected. Your CDP-130 can do this. But I think you can expect 48 notes on a plain piano sound.
I investigated the new range of Casio pianos recently, in a search for something lighter to carry than my Kurzweil PC3X. (You just DON'T take your car to a central London gig any more, I need something I can carry on my back.) I was most impressed by them, particularly considering Casio's previous reputation for being cheap-and-nasty and the low price.