I've tried several different combinations of head units, speakers, amps, subs, etc, trying to find that perfect sound. Then my oem battery went dead. Figured I try an Optima yellow top, but it wouldn't fit in my little civic (not without mods). Then I found this and it gave me a near perfect sound! The vocals opened up, bass is tighter, soundstage presence! All from just a better battery. Love it!!