Advice needed to choose correct H/U

Hey guys,

Soon i will be replacing the H/U in the Clio and need to understand what the best bets are to be honest.

I dont have an Ipod just because....i dont and thats sort of that really, i dont use one and never have.

I am sort of interested in a USB H/U if thats the correct way of putting it? From what i understand, Alpine and Pioneer make players where you can literally just plug a usb flash drive into the front of it and all your music will play through that, is this correct?

Also i download on Itunes alot and the file type for this is slighly different as i understand it? Will these units have any problems playing these tunes?

As for the stalk adaptor, i will be getting one. Does this literally just plug into the existing stalk loom and then into the back of the unit in order to retain the controls?

Thanks, all help much appreciated!