I believe Kr4 is right. You have a problem with mismatched gains. I believe the sensitivity of the ARC was 1.9 volts in to get 100 watts out, and the ASL is 1.7 volts in to get 200 watts out. So for the same input you are getting more than twice as much power from the ASL, this makes the system sound bass shy since you are used to the lower sensitivity. The new, more powerful bass amp will likely have the same gain as the older one since they come from the same family so this will not help. As Kr4 said, you will need to pad the input to the ASL to lower it's sensitivity or adjust the crossover, if it can be.