Thanks for your suggestions CongaCaja.
Well, after long inquiries I finally decided to leave the Performer option and buy a LP Classic tumba. On
http://www.anydrum.com they sell it out for $ 299,95. There's also an Italian LP endorser percussionist that could get it at a reduced price. So, now I'm just thinking if it is more advantageous ordering the tumba in USA or buying it here in Italy. In the next days I will come to a decision.
As far as natural heads concerns I have never tried them on congas. My experience with natural heads just restricts itself to African drums (djembe), that have a goat head, thinner than congas one. That sustains much more all drum's tones. But, as you know, employment and aim of congas and djembe are different each other.
I will try anyway to get more information about natural heads for congas (do they provide the drums' tones with something particular?). You never can tell, If one of my hand-picked heads breaks I could think to replace it with a natural one!
Pasqua