Thanks for the fast respone EgonOlsen. I recall you said in a message that shaders are somewhat slow on mobile devices... do you think a normal map shader will slow down the framerate significantly ? Considering the fact that mobile devices also don't handle "high" polys very well, that's why I was going to use a normal map in the first place, to fake real topology...
P.D: I tried a normal map of a 9000 tris rotating human face using libgdx with specular, diffuse and ambient lighting and it was really fast (60fps, limited by vsync).