Actually, Amazon's a really good place to comparison shop, since most major carriers have their plans on there. I got really overwhelmed with all of the choices when we got a new mobile phone for me recently, and Amazon saved me from having too much of a panic attack over it. I also found that the online sites for At&T, Verizon, etc. had *far* better plans than they offered in the stores. Way fewer charges and so forth for set up and things.

Anyway, good luck! Going to play with the phones in person sounds like a very good idea, too. :)