I was using a TRRS connector that came standard with my I-Phone and had buzzing issues. Switched to a TRS connector and have had 0 problems. However, either connector worked just fine with my Zune HD.
I am actually looking into doing a bluetooth solution but will try the cable first. Cheaper. Anyway, if anyone is interested I am looking at buying a BluBridge mini-jack Rx by Miccus. It is a bluetooth receiver that plugs into line in. I can use the built in power plugs on the radio to keep it charged. Not sure how long my Iphone4 will last in bluetooth mode but I can always leave it plugged in when not changing music. I like the idea of having the phone close to me to change music.
Will post back on both solutions.
Off to radio shack...