wow... thank you all for your replies, you've definitely answered all of my questions.
I have new ones now, of course
So this means I would be able to connect the HiFi speakers to the computer if I had an amplifier (of satisfactory quality) which would be put between the two? Of course, that would require some necessary tweaks and I would actually end up building a receiver? And another of course: if not building a brand new amplifier from the very beginning, I would have gotten it from another HiFi receiver, and that again would make no sense doing because the amplifier, as ShadowTek said, is the main value of a receiver and then I could have just as well connected the speakers through the existing receiver?
Sooo, if the answers to the above questions are all "yes", the only sane thing to do is to buy a new HiFi receiver - that would actually prove to be the cheapest solution then?
Once again, thank you all for your time and patience