besides the power issue you might have, there are other things to look at. do you have a good, solid ground on your amp?
If the ground is too long, loose, or not anchored tight to bare metal, you can have this happen.
How are your subs wired? If your OHM load is to low, you can have this problem
Is your box built properly? If your port tuning is off, you can tear up your subs.
definately get the big three done asap. Your 4g power wire isn't helping you much, if your factory ground wire at your battery is 8g.
this is just the start