If you're interested in affiliating with groups other than the 26 NPC sororities (not that that those are not good choices!), I would also suggest looking into Omega Phi Alpha National Service Sorority (
www.omegaphialpha.org)
This would be different from most of your options because as a service sorority, OPhiA is primarily a service organization, secondarily a social organization. We feel that this makes us stronger
We recently absorbed a local sorority in a situation similar to your own, so these kinds of transitions are something that we are familiar with and treat with respect. If this is something you would be interested in, I'm sure that our VP of Expansions would love to talk to you.