Aftermarket speakers aren't designed to emit low bass frequencies. Not sure if you are running a component set or not, so I am assuming that you are. The crossovers that came with the BA speakers eliminate that low frequencies. Its specifically designed for that tweeter and mid for best performance and sound quality. You are beating a dead horse trying to find new speakers to replace your BA set to achieve that bass you desire. Get a small sub.
Your stock speakers receive a full range of frequencies. Sure, they emit great bass, but sound like poo and dont get that loud. Get a small sub.