this x2. Really it's not that hard to get tones that match your EQ bands and simply listen for where you major peaks are. Cars are bad acoustic environments, you'll hear the bad ones when you hit them. If your not 100% sure loud it should be, just realize every tone gets a little louder up until 4k or so to most people. If you need a reference, even a cheap set of headphones (like the 10 dollar ones) are still a decent reference point as they'll be ALOT closer to flat than any basic install without EQ.