They're about $100+... it won't give your subwoofer MORE power, it'll allow your Amp to run at it's full potential (with larger amps, bass hits can drop voltage... and available power) You MIGHT see a difference... what wattage is your amp? Here's one that would work for a smaller amp If nothing else, you will save your electrical system... I've never used one... but I've watched my headlights dim many times... LOL