Migrate to Exchange 2003

Assuming everything is good to go with Active Directory.
Have an Exchange 5.5 box called Exchserver. Has a invalid site name for Exch 2k3. Creating a new server EXCH2K3 on a new site. Will install it and copy over the mail from EXCHSERVER using the migration utility. Disconnect EXCHSERVER and create another Exch 2003 server called EXCHSERVER. Check DNS, make sure everything is ok. When a client signs on, will it just talk to the new EXCHSERVER, which will redirect the client to EXCH2K3? Should I consider bringing up the new EXCHSERVER as 5.5 in the same site as 2003? Is this a good option?