Ok, I finally made it! I had my car dismounted and remounted , and now my installation is complete.)
I just wanted to thank you all for suggestions and recommendations. From you I had great ideas to begin with and excellent info to use as a comparison.

So, after talking with my firend and installer, considered room available and costs and performances, I finally got this:

Front Speakers: Hertz Space 6K 25 Kit ( midwoofer Space 6 + tweeter HT 25 )
Rear Speakers: Hertz Energy Coax ECX 690
powered by
Amp MTX Thunder4244

+

Subwoofer: Impact CBX 112 (a picture is here)
powered by
Amp MTX Thunder 6152



I should have some pics up on riocar.org as soon as I get my gallery approved

Now what matters most: the sound is simply wonderful. I am impressed by the quality and pureness of it. I admit that it exceeded my expectations...