Recommend a GPS unit with these features?

Can anybody recommend a GPS unit that has the following features and is as inexpensive as possible?

1 Spoken turn-by-turn directions
2 Lifetime map upgrades
3 Traffic alerts
4 Adapter available so that it can plug into USB port as well as car power port

Also it would be nice if it had these 2 features:

5 Warnings for traffic signal & speed cameras
6 Expandable memory

Thanks for any help.