Those RCA jacks would be for output. Most HU's have some preouts for amps and whatnot (I've never modified my stereo beyond the HU, so someone else can clarify this
) .. mine has three sets.
I have an Alpine CDA-9807 that is compatible with the iPod interface, but I was too cheap to spend the $100 on it. Plus, the crappy display on my Alpine (not dot-matrix) would have been harder to navigate the iPod anyway. Instead I just bought a $20 proprietary cable that turned its computer interface jack into a pair of RCA jacks, and took an RCA-to-minijack to hook directly into the iPod. Works fine, and I keep the iPod just under the e-brake so it's easy to thumb around.
If you know the model of your Sony, you can look up on the 'net and see if it has input jacks in the back ... or try the Audio forum on CEG.
