I'm going to use an admin solution like EMS http://ems-hitech.com/mymanager/ to manage the database and users because I can't find any ONE solution that does both database user management and ER diagraming (if you know of one, please let me know).
I have also thought about drawing solutions like Visio and SmartDraw because if I'm going to use EMS I may get into problems using two solutions that both have the abilty to alter table structures (e.g Case 2 and EMS or Datanamic and EMS). If I stuck to EMS for the table structures, relationships, etc and a drawing solution (that can't alter table structures) then I know I am safe. I guess the only thing I would miss out on is reverse engineering (which would be useful).
Any advise on the best way to go would be most welcomed.