help with 2006 A200 upating music system

[Thenunn]

Hi I'm hoping someone can help me I have a 2006 a200 elegance . It has the audio 20 (2) with the ipod intergration kit in the glovebox and a mercedes bluetooth thingy in the centre arm box for the phone. It also has a wierd plastic knob/cover on the center console under heating controls.
I would like to add bluetooth music or use my sony phone to access my music..so here are the questions...
Is there an adapter for the ipod kit to allow this ?
Can I change the ipod kit for a bluetooth or aux ?
Would the audio 20 (2.5) fit straight in or would i need other bits ?
What would be the cheapest why to get bluetooth music or music off my phone (without one of those silly cigarette lighter things )
Does anyone know what this cover /knob is for ?
Thank you

first pic is knob...2nd is where my ipod lead goes through back of glove box

 

[Thenunn]

ps ...would a unit from a 2011 aclass (man ref :
A1699002000


fit ?

 

[GLK]

As you're replacing your Audio20 with an NTG2.5 version (as per other thread), it might be a good idea to replace the trim, to get rid of that less than pretty non-OE cover/hole.

This should fit the bill, and not terribly expensive:

2005-2008 Mercedes A class W169 heater control surround dash trim | eBay