The question I need to ask you is how you want to run your SVN server. If you are accessing SVN via Apache(mod_dav_svn), then you'll need a GUI which allows you to manage the Apache authentication, which could vary. If you are using svnserve, then you need something that edits the built-in permission of the repo. I recommend the Apache mod_dav_svn method. You can have Apache connect to an Ldap server. Then it is possible to allow Windows users to connect quite painlessly. Managing them is also somewhat painless (If you know about AD that is.)
That being said, I recommend websvn: http://www.websvn.info/
Perhaps the thing that websvn is missing that you want is a way to make new repositories. The command for this is very simple. If you have Apache mod_dav_svn set to use SVNParentPath /path/parent instead of SVNPath /path/singlerepo, then you only need to type:
svnadmin create /path/parent/newrepo
on your linux server and with the user apache runs as or chown the files after.