If you get the RNS 510 I can guarantee it will be one of the best mods you could ever buy for your car.
Absolutely amazing bit of kit!
You will need a Bluetooth module if you want to connect your iPhone.
(you will need the correct model number)
Also with the RNS 510 try to get the latest version with LED screen. The versions go from A,B,C..... and I think they are on F or maybe even G now (not sure)
For Extra help there are a few members here that really know there stuff. (VRStu, MortyGtdi,Eddie-NL)