Boundinashes

Hello, I own a 2011 Scion XB rs 8.0 and just recently purchased the alpine nav ready premium head unit for my car. I was curious as to what part I would need to "activate" the navigation on it. I searched for various parts online and they range from $39 - $600.

http://www.rileyscion.com/PricingMenu2 has a list of different navigation parts, but i'm not sure which one or part number I need to have.

My head unit is part number is:
PT545-00111 or PT545-21100


Any suggestions ?

Thanks !