I just installed a similar system in my Scamp. I used my Ipad2 with no Head Unit. It is a cheepooo set up and I only have about $300.00 total into the whole system including wires and cabling. This of course does not include the iPad. I do not leave the iPad in the car. I have cellular on it, music through my iCloud account, on the device itself and can hit Pandora or anything on the net while mobile. It of course also has Wifi.
I used a 7 band Parametric EQ for the iPad input to turn on the 4 Channel Amplifier. I have 6 speakers total. 2- 6x9's in the rear deck, 2- 6.5" I put in end caps mounted off the A Piller cage bars low by the kick panels and then 2- 4" in the dash. It came out nice for what it is an sounds a heck of a lot more than a $300.00 set up.
Pictures etc start on post #842
http://www.forabodiesonly.com/mopar/showthread.php?t=224605&page=34