I just installed my bassling in my 2005 Crown Vic.

I had the same problem in my grand am had a rockford 1200watt pushing 2 rockford hx2s. Turn the car on and speakers would hum and turn it off same thing that used to aggrevate the sh** out of me I added a 1 farad stinger capacitor in line from my battery connection to my amp and added a good crossover and I was in good shape until I got rid of my system. I could only turn my gain up around 10% drove me nuts but check out something like best buy or crutchfield online and you'll find what you need. Hope this helps