The only Nokia that will work with Cingular's 3G is the N75, which is not currently out.
There are 3 frequency combinations for 3G:
Europe: UMTS 2100 (uplink and down)
Cingular UMTS 850/1900 (uplink and down, but not dedicated. I.e. you could use UMTS 850 for both up and down, or 1900 for both...