I'm seeking suggestions and insight on how other people approach their directory structures for a member subscription area of a site.

I am working on a site in which the client wants to add a paid subscription area for greeting cards. The content would differ from the main site. It's a Wordpress website. Would the recommendations be to place the area in a subdirectory of the same wordpress install or create a completely new wordpress install database with the same theme look?

I'm thinking of using eMember for Wordpress. Any experience with that?