I would stick with a Garmin. Very reliable and easy to use.
If you buy a cheaper model...you will be limited by the number of maps that you are able to store...just something to keep in mind.
I paid 10% under dealer cost for mine because I was a Garmin employee at the time. It cost me around 300.00. I was able to get all of Arkansas, Louisiana, parts of Missouri, all of MS, and over to the Dallas/Fort Worth area loaded.
I have never had a bad experience with mine. I love the time of arrival feature.