SBS 2003 server along side SBS 2011. Or what are the options?

Hello all,

Currently have a SBS 2003 server with around 30 users. Will be getting a new SBS 2011 server. What are the options to keep an old server running along side SBS 2011 for old applications like Dynamics and Blackberry server? Is it possible to demote SBS 2003 as domain controller and keep it running as a server with SBS 2011? SBS 2011 probably needs to be a premium edition, right?

Thanks.