I have recommended 2 ways to update your iDevices to iOS6 officially, via iTunes or OTA. In case you feel to download the official firmware for your iDevices but you don’t have it on hand. You can try to download the iOS firmware package directly from Apple server. Below are the complete download list for different iDevices, includes iPhone 3GS, iPhone 4 (AT&T & Verizon) , iPhone 4S, iPad 2 (Wifi, AT&T, Verizon) , iPad 3 (AT&T, Verizon), iPhone 5, iPod 4th and 5th generation. These are ease for your future firmware restoration as well as jailbreak job.

iPhone 3GS – http://appldnld.apple.com/iOS6/Restore/041-7173.20120919.sDDMh/iPhone2,1_6.0_10A403_Restore.ipsw

iPhone 4 (AT&T) – http://appldnld.apple.com/iOS6/Restore/041-7177.20120919.xqoqs/iPhone3,2_6.0_10A403_Restore.ipsw

iPhone  4 (Verizon) – http://appldnld.apple.com/iOS6/Restore/041-7179.20120919.bDw4g/iPhone3,3_6.0_10A403_Restore.ipsw

iPad 2 (Wi-Fi) – http://appldnld.apple.com/iOS6/Restore/041-0804.20120919.9SgHU/iPad2,1_6.0_10A403_Restore.ipsw

iPad 2 (AT&T) – http://appldnld.apple.com/iOS6/Restore/041-7165.20120919.eZTyh/iPad2,2_6.0_10A403_Restore.ipsw

iPad 2 (Verizon) – http://appldnld.apple.com/iOS6/Restore/041-7167.20120919.y2ard/iPad2,3_6.0_10A403_Restore.ipsw

iPhone 4S (iPhone 4,1) – http://appldnld.apple.com/iOS6/Restore/041-7181.20120919.lEuOK/iPhone4,1_6.0_10A403_Restore.ipsw

iPad2,4 (iPad2,4) –  http://appldnld.apple.com/iOS6/Restore/041-2187.20120919.vmGkW/iPad2,4_6.0_10A403_Restore.ipsw

iPad 3 (AT&T) – http://appldnld.apple.com/iOS6/Restore/041-7161.20120919.5CyjO/iPad3,2_6.0_10A403_Restore.ipsw

iPad 3 (Verizon) – http://appldnld.apple.com/iOS6/Restore/041-7163.20120919.19UEI/iPad3,3_6.0_10A403_Restore.ipsw

iPhone5,1 (iPhone5,1) – http://appldnld.apple.com/iOS6/Restore/041-7169.20120919.5Mial/iPhone5,1_6.0_10A405_Restore.ipsw

iPhone5,2 – http://appldnld.apple.com/iOS6/Restore/041-7171.20120919.doJ1e/iPhone5,2_6.0_10A405_Restore.ipsw

iPod5,1 (iPod5,1) – http://appldnld.apple.com/iOS6/Restore/041-3517.20120919.9ln3Q/iPod5,1_6.0_10A406_Restore.ipsw

iPod touch (4th gen) – http://appldnld.apple.com/iOS6/Restore/041-0807.20120919.soT6X/iPod4,1_6.0_10A403_Restore.ipsw