trust me, don't waste your time on the ones that they are currently selling ($60 for the set i believe).
I bought a set, had to be exchanged twice due to heat failure.
if you don't mind the "shower head" look (see pics), then all you need to buy is:
All can be had for about $30, $35 bucks. You can search http://www.car-part.com/
for your GPS Antenna