i'd try the following:

1) Separate the power for monitor and head unit (HU) with upgraded lines directly to the battery (w/ fuse, etc.)

2) Reduce the length of RCA's and pay attention to the signal direction for the cables (my monsters were directional, providing arrows to indicate which end was for the HU and which end was for the amps...).

3) Change the ground for the HU. I wouldn't use the stock harness for that. Behind your HU there's a threaded bolt welded to the firewall (w/ nut). Use a dremmel and expose metal. Ground to that nut/bolt.

Steps 2 & 3 greatly reduced my alternator whine in my own setup.

Best of luck.

-biju.