Thanks for the info. I am interested in getting a GPS to permanently mount in my car that can be easily turned on and off via serial or via the amp remote line on the empeg. The GPS that I am currently using has a button that needs to be held down for a few seconds to turn it on so any sort of permanent install would be tricky. However, I don't really want to spend the money for a differential unit unless it really improves navigation. Is there a more affordable OEM stile unit that is meant to be controlled by another device but without the extra WAAS features? Or would it be worth it to spring for one of the units mentioned above?

Thanks,
-Mike