What I know is that the Storm 9530, will not work on Tmo EDGE network. You will get the GSM part to make calls but no data.
The Storm 9500, is a GSM and will work on Tmo EDGE network. Problem is that the 9500 is provided by Vodafone; which is a European provider. So if you can get that model and unlock you should be good to go.
If you know where to get one, point to that direction...LOL