The default behaviour of Stuffit Expander is to expand into a folder in the same location as the archive.

However, there is an option in the Destination pane to change this so that it prompts you for a destination folder, into which it will merge the archive contents.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)