When I bought my 05 GTO, the subs were already blown. They still work and sound ok at low volume, but when I turn up the radio they start rattling like crazy. Question is, can I hook up aftermarket 6.5" 4-ohm speakers and keep the factory amp hookups? If so, what brand does everyone recommend?

For reference, I had already replaced my front and rear speakers with some 3-way Kenwood speakers (100x better than stock). I just want to keep some decent bass with the new speakers.