Hi,I'm thinking about getting a portable GPS unit for someone sighted. It should have turn by turn directions. Synthetic speech for street names would be nice, but is not essential. It should have quick acquisition time. I've seen a Magellan unit that takes a really long time to acquire the position. Also, I'd like it to come with the whole U.S. maps and POIs built in. It should also have a battery so it can be used handheld or if the power source in the car is temporarily unavailable. Any suggestions? Peter