Steer clear of the "Mio", as it tends to be very anti-intuitive and just plain daft. Maybe I had been too spoiled by using a TomTom, but when I tried to use a Mio it was a fucked experience.
TomTom is something I can testify to. Right now, there are two low-priced models - Best Buy, at last look, has one for around $100 and the other for about $160 - that's the one I have, and will personally vouch for.