if you can use cingular, i would. i have an '05 rx330 and i use me bluetooth.
i have the motorola V551. it works great. of course i'm speaking only on the fact that it works, service areas vary as reception goes. as far as i know that is one of the only bluetooth capable phones that cingular offers, that is why i got it.
my only complaint is the phonebook issue that has been mentioned on different threads. the fact that you can only add/synch one entry at a time is kinda time consuming, but IMHO it is worth it.
i'm in southern california and have had good luck w/ cingular, i used to be with nextel (huge mistake) and i'm glad i switched.