I had the same issue about month ago. We were migrating and starting second server, so I did some research and case study to determine if one-database solution would work.
Unfortunately single database would make more mess, than good things. Every server assings different GUIDs (they are created according to the server IP), so every client playing on both servers would be duplicated in the database. Finally, echelon and xlrstats would be messed up terribly.
Better solution is to create separate databases. Slightly more work needs to be done, but all in all it's much easier. Then you can have echelon taking care of multiple servers (like here:
http://img7.imageshack.us/img7/4276/obraz16x.jpg ), and you can have separate xlrstats for both servers.