Why would you consider a BB? None of their phones are competitive.
If it is for mail, try MailDroid or K9 Mail. If it is for BBM, I "hear" that there are BBM compatible Android apps available, but they are not on the market. I posted about this over on AndroidCentral, but don't have the post handy.
My wife has a Storm 2 (she and I both had a Storm 1) and you couldn't pay me to use that piece of .... again! The only thing propping up RIM right now is the glacial pace of corporate IT change. Once businesses really begin to catch on to how well Android and IOS can meet their needs, RIM is finished... unless they can change SO many fundamental things about their business. Especially their proprietary approach to their products.
Is there a specific reason why you are selling your DX? I don't see how it makes sense to sell your DX and then pay (more) for a new one since it came out only a couple months ago.
FWIW, if I were to get a new phone right now, the only alternative to my DX would be the Samsung Fascinate. What a BEAUTIFUL screen it has!
Scott