maybe you dont have to integrate it in to one db, just check each db one after the other for the login details...true things would have to be added to each db to account for cross usage (ie i download a maya tut, that needs to be recorded in my recordset)
another thing to get around the username problem:-
Techi (LW)
Techi (MAX)
Techi (XSI)
or
Techi
Simply LW
Registered Member
Avatar
Techi
Simply XSI
Registered Member
Avatar
just some thoughts of mine