alpine stereo system problems

[9C1 VT V6]

hey guys I have just installed the following stuff into my vt alpine type s 6.5 inch speakers in all doors components in front and two alpine type s 12" subs in the boot with an alpine 1100w mono amp and the speakers are running off an alpine 640w 4 channel amp. once all this was installed I noticed that the hole system crackles at about medium volume and my battery light and interior light flickers I got told that it was the headunit causing it to crackle so I went out and bought a new one an alpine one I installed it myself only to find out that it still crackles and to add to the drama the headunit wont turn off when I take the key out of the ignition it just stays on... soo any way I got the crackling checked out and I have been told it could be something wrong with the alternator or the battery and that the stereo is lacking power to run it but what I dont get is I used to run alpine type s 6x9s in the rear shelf and they worked fine of the 4 channel amp and then eventually they started crackling I thought I had blown them so I went out and bought all of the new stuff above only to find out once it was all plugged in that it was still crackling! all the earths are fine the wiring to all amps and speakers seems fine soo everyone I've seen has narrowed it down to either the...

-4 channel amp is broken
-alternator
-battery, which is pretty new...

problems...
-hole system crackles
-headunit wont turn off when I take key out of the ignition
-battery light flickers on and off

so if one of you guys have had a similar problems and knows what it could be please tell cause I'm at my wits end with this thing and I dont want to pay for something that ends up it isn't the problem i'de rather pay for one thing to fix it and be done with it!

thanks guys!