I reccommend the StreePilot c330 ($600-ish) or better. The SP i series have tiny little screens and no touch screens. Transflash memory cards are proprietary and are very expensive. c320 ($500-ish) doesn't have built in maps so you need to connect it to your computer to transfer map files any time you decide to take a long trip... c340's ($750-ish) extra features (namely traffic detection) requires a service fee (about $8/ month)...
TomTom Go700 is nice, but pricy ($800-ish). Lack of support is frightening. There is not enough information about its units online and customer service does not return emails. Cannot get to a live operator on the phone. Go300 ($600-ish) doesn't have any built in maps. Some people had trouble with the routing and menu navigation of these units.
Magellan 300 is cheap. Menu functions aren't all that great. the 700 is better, but Garmin's units are better for the same price.
There are many more units out there, but you should look for a fast processor and built-in maps if you do a lot of travelling across states. The Garmin StreetPilot line is the best out there for North America right now.
