Okay, I'm still not getting it. You have a 250 amp alternator and a 500 amp sound system. When you turn up your volume, the battery should drain and the light should dim until the battery goes dead. End of story.
What am I not getting here? The power to the amps comes from the alternator + battery. If you pull more than the alternator can supply, the battery supplies the rest until drained.
If your battery is not routinely going dead, you aren't pulling near the amperage you think you are which means you are over fused.
---------- Post added at 10:54 PM ---------- Previous post was at 10:30 PM ----------
Just received this from the O.P.:
If you would read number 5 i said NEW STILL IN BOX NOT IN TRUCK thats way i'm asking for help to make sure i'm good on power. Plus even if it's 500 amps it will not pull near that amount.
Now why did that post get closed?"
-->I have no idea how it got closed. I didn't do it. Sorry to wreck your post. Good luck with your system.