Ground/alterntaor Whine

Hi,

I just installed two Visonik Amps (V2118 and V417SX) One is a one channel while the other is a four channel. The One channel peak output is 1200 Watts while the four channel peak output is 800 watts. After reading some post and my recent question being answered, I know I have to upgrade my power wire to four gauge. At the moment it is eight gauge that is ran to a power distribution block. I also have to redo the ground wire and change it to four gauge. I am gettig terrible alternator whine, I mean it is really bad. I used the speaker level inputs off the V417SX to tie it to the factory head unit. I used a line input to RCA converter that was connected to the left and right rear factory speaker wire to tie the V2118 to the factory head unit. I was going to check to see if someone made a Line to RCA converter that ties directly to the factory head unit, but no luck at this time. With that said, on one side the power cable, line level controls, and two of the door speakers are ran togther, so if anyone know of any material that I can use to shield the speaker wire please let me know. This is what I plan to do tommorrow: Upgrade the power cable to four gauge, Upgrade the ground guage to four gauge but run this to a ground distribution block. Get some RCA cables that has a ground wire and ground these separately. Please let me know how I should proceed.