Just so I'm sure you know... If you buy a phone from Cingular, it will need to be unlocked before you can put another provider's SIM in there. Motorolas are apparently easy, but I've never unlocked one. I have the equipment for older Sony phones, but I don't think it works for the newer models.

If you take a stroll in chinatown in NY, you will find a bunch of shops willing to unlock just about any phone for like $20.