5 Digit Mixing/Mastering Tools

I listened to the Final Mix in three different cars. 2005 Honda Odyssey, 2005 Ford Focus, 2005 Kia Spectra. I was amazed at how different things sounded in each one. Certain sounds (like snares) would be 10x louder in one car, but in the next the bass would be overpowering. I took copious notes, tweaked each song, then went back to listen again.

I did this about 10x. My lady told me I'd never be finished and there'd always be something else to fix.

She was right. I listened to a song by Interpol in the Honda, and I could barely hear the vocals, which sounded normal on iTunes. After that, I felt better about the inconsistency. This music wasnt made for car stereos anyway! These songs (on headphones preferably!) are more of a background for PHP/MySQL programming, painting, or playing chess.