Wow, boys!!!!
I'm simply overwhelmed by the number, the speed and the quality of everyone's replies... Yeah, I have to say it again: I'm really speechless!!! Thanks a lot to everyone! Now I'll take my time to read thoroughly (and understand them...) every sigle reply, but the first glimpse is sufficient to make me sure you gave me all the informations I needed ( and even a lot more...). If I don't understand this time how displacement-maps really work ...it's mandatory I start looking for some brain-upgrade kit.
Thanks to everyone,
                                       Alberto