When I signed up with T-Mobile, I got the Samsung E715 which I loved. It has everything you need - awesome external display, mp3 ringers, camera + flash, built in antenna. I was able to talk down the price, also, by saying that a kiosk in the mall had a price of $230 and ended up getting it at $210 i think. Usually managers can only do things like that, tho.
Still, go for the E715 :-D
*And also, if you call up customer service they'll tell you if you're eligible or not for any upgrades and such. I didn't even know you could email T-Mobile :P