Not sure exact HP that stuff will add, but I do know on a Honda, weight matters! So if your stero is 400 lbs (thats alot of shit!), then yea, its def gonna affect your performance... From when I drive just me in the car, I can tell a difference when I have a passenger... U really dont need to ditch the stero all together, just slim it down a bit... What all do u have? I have 2 amps (low amp, mids/highs amp), and a JL 15" sub, and my car seems fine... Probably about 100 lbs total max...