Dave, I also have the whine, and I have traced it to it's cause.
Seeing that we both have the same setup, I thought I would share my findings.
Went to an audio installer and questioned the fitter about it and he said it's prolly a bad earth or insufficient earth.
Then I told him about me using inline boosters and he said that that might be the cause, so I went home and disconnected the RCA's from the line boosters and connected them direct, sure I lost some volume, now having to turn up to 40-ish, but the whine has gone.
So when I get a chance, I'll accuire some ground loop isolators and add them to the grounding cables on the line boosters and see if it helps.
Will keep you posted once I get around to it.