I say go with the letters you have, even if they do sound a bit like Kappa Kappa Gamma or Alpha Gamma Delta. You can't avoid sounding like some group out there. And there are plenty of groups that sound alike:
AEPhi and AEPi
Sigma Kappa and Kappa Sigma
ADPi and AOPi
ADPi and ADPhi
Theta Chi and Theta Xi
AEPhi and Alpha Phi
Chi O and A Chi O
I even get Delta Zeta and Kappa Delta confused all the time, and they don't even sound that much alike!
I've never really gotten this "being so protective over my letters that I don't want any local group to have anything that sounds like them" thing, but maybe that's because it's hard to find anything that sounds too much like Tri Delta. "Delta Delta Alpha" just doesn't have the same ring.
