To choose a right GPS, you can have a look at this article:
http://www.maps-gps-info.com/htcgp.html
And I got to know that the Cobra GPSM-4500 had a price drop from $360 to $324, seems quite nice you can have a look at it.

Here is a link that might be useful: Cobra GPSM-4500

I suggest buying the Honda unit. They are very friendly and much easier to use with their larger displays and such than a portable unit. They also can't be stolen since they are part of the car (not easily anyway).

If you do want to buy a portable unit, Garmen units are superb from ease of use. Like the Honda unit, they are pricier than the competition but work quite well (I have two).

Garmin 680 - 299 at Costco if you're a member. I love it! Keep checking on Fatwallet or Slickdeals and be patient. This deal comes around once every couple of months or so. For general reviews about the GPS unit check the link below.

Here is a link that might be useful: Amazon Garmin 680 Reviews