(weird, why is ordering a new computer so scary? ...afeared of the inevitable set up hassle, wire tangle nightmares, configuration times and brain breakers ahead.. yes even with Mac.... I´m afraid I will be back here.)
The iMac need only have one cable (for power) if you get the version with wireless keyboard and mouse.
Good luck at the 'Store. Help is at hand here for any other unforeseen events.
Applemacster