Well if you are going to start with Polish music, you have to start with Czeslaw Niemen and Marek Grechuta.
Some more modern ones I like are: Kult/Kazik, Republika, Piersi, O.N.A., Hey, Myslovitz, Goya, Kasia Kowalska, Edyta Bartosiewicz, Ania Dabrowska.
Also a lot of good Polish Jazz was made in the 60s, probably the biggest name was, Krzysztof Komeda.
I cannot help you enough for providing those Polish singers. I have found a number that I have loaded on YouKu. Best Regards.