If you go to the Web site below and look under Airtran and flight cancellations, I think the rules you see should apply to you. That is, they should accomodate you on their airline at no cost, which they have offered you but you don't want to go through Atlanta. But, if it's not acceptable to you, they are also supposed to offer you alternate transportation on airlines with which they have agreements, which includes USAir.

http://www.quiltropolis-travel-desk....of_the_Air.asp

The thing I'm not sure about is whether these provisions apply only if you're en route, or whether they also apply to cancellations that are well in advance. Perhpas some Rule 240 experts could help??