Restricting Page Access to certain Users

I would like to restrict certain pages in my site (I’m using WP as a CMS for a site rather than for blogging) to certain registered users (clients) that would be created manually in the Admin side of WP. I plan to create a specific template for restricted pages with a conditional based on ‘get_currentuserinfo()’ – unrestricted pages won’t include this. These registered users will NOT have access to the WP backend. Can I create new user levels, “client”, so that rather than hard coding information I can create them in the Admin pages? Is there a plugin that would have this functionality – I haven’t seen on yet that prevents access to the backend.
Regards, Edward