Well, if anything, get the Dual headunit just for Iplug capabilities, but don't go cheap on subs or amps. MANY manufactures make the needed hook up cables, like blaupunkt, sony, and alpine for an ipod (range in price from 20-70 bucks).
Th eonly thing that sucks with the dual unit is the lack of preouts, and the one it has will be used to power the ipod. Does it have sub preouts? I can't recall if it did, or not.
EDIT:
Don't get mad at us, either. you didn't STATE YOU HAD TO BUY FROM BEST BUY.
