Pay attention to RMS ratings, not max wattage ratings. Think of RMS as the average amount of power that your speakers can put out. Max wattage is what they might be able to handle for a split second. Run them at that level and they'll die. When choosing an amp, match the RMS output of the amp to the RMS wattage of the speakers. You can bridge two channels for your sub. Look at the specs for the amp and they'll tell you the bridged output power. You'll do better choosing an amp with a slightly higher RMS rating than your speakers than if the speakers have a higher rating than the amp.