Suggest that you take a look on the Net for pricing. Magellan, Garmin, and TomTom make good automotive gps units. Depending on the features you want or do not want will control the price.
Features that were important to me:
1. Built in battery. My Garmin has a battery rated to last five hours. The logic is that if I am out beating around on back roads and I get stuck. I can use the unit to guide me while hiking out.
2. Bluetooth. I chose a unit that has Bluetooth and I can use my cell phone hands free with it.
3. The ability to add waypoints to the unit. My unit has a SD card slot, and I took a number of stored waypoints from my computer and put them on the card and installed them in my automotive unit.
4. Mounting. At least two States have laws prohibiting windshield mounts. My Garmin has a dash mount.
5. High sensitivity receiver
6. Plug for external antenna. Last week we took my wife vehicle to the City. I am not allowed to put a base on her dash so the unit set in the back seat. This is not an ideal location for a gps but under less then idea conditions the voice gave us turn-by-turn directions to were we wanted to go.
From what I have seen Magellan automotive manuals are not to bad. I have no idea about TomTom manuals. My son loves his older TomTom. A friend purchased a Magellan in a higher price range then what you are looking for. I am impressed with his Magellan. The Garmin manual for my c550 was nothing to write home about.
I have done business with both these vendors:
http://www.tigergps.com/?GCID=C19426X001&keyword=1http://www.gpsnow.com/garmin_nuvi_gps.htm