The Alpine 9856 in my car has been working great with various devices like my Sirius StarMate4, and iRiver MP3 player.

The only two things I needed were RCA cables for the inputs and a 3.5mm to RCA cable. Select AUX as the input it was done in a flash.

 

Get an FM modulator.

 

An Fm mod will limit the frequency response to that of FM. Limiting is not what you want. There are lots of decks that have Ipod inputs. Some with just mini plugs for audio only, others with USB for full function control of your ipod.

 

Inthe new sony brochure just about every deck comes with atleast the aux.input for an mp3, some have a usb aswell, and other have bluetooth, lol kinda sounds like an advertisement doesnt it.

 

The new Pioneer Premiere units have aux input and IPod input (cable included) + 3 preouts, exactly what you need.

 

The nice thing about RCAs is they are low voltage/high impedance..... that makes them more or less idiot proof... If you hook them up incorrectly, you arn't going to blow anything up.....

 

Yes I understand this but if he has a HU with one set of RCA's out Im not sure if he is worried about this factor. FM modulators will provide an inexpensive way of connecting portible devices and is only as good as the FM tuner agreed. But is much more reliable then the wireless FM transimiters without having to lay out more cash for a new HU. I like to let someone know about all avenues before costing them money. But yes its only as good as your tuner.