There is a lot of controversy surrounding capacitors in car audio and if you are running a big enough system to warrant a capacitor you should probably be upgrading your battery and alternator as well as doing "The Big 3." That being said, I purchased this simply to level out the load placed on my car's electrical system (one constant load rather than a bunch of big ones) and to hopefully provide a little extra juice to my amp. If it reduced or eliminated headlight dimming then that was just icing on the cake.
Charging took a while, I stopped to let the resistor cool many times but when it finally got charged up I pulled the sides off (very stiff, be careful not to break anything) and attached it to the backside of my box and got everything wired up. I was blown away by the difference it made, I got a ton of extra bass and it was much tighter and more precise than it was before. I waited until dark and took it out to see what difference it would make in my headlights with stock alternator, normal battery, and The Big 3 done and with my high beams on and the volume all the way up I could not see any dimming. I let it idle to see if the drain would dim the lights when the alternator was not putting out as much power and I still did not notice any dimming. My Boston Acoustics GTA-800m used to dim my lights pretty bad, especially at idle on high beam, and now it doesn't seem to be an issue.
I bought and tested this cap as objectively as I could, I had no prior bias as to whether or not it would affect sound quality or headlight dimming and from what I have seen in my own car I highly recommend this because it gave me much better sound quality, more powerful bass, and it eliminated my headlight dimming. It seems expensive until you see and hear the results, then it becomes a bargain!