DuckDuckGo can search using almost any search engine anonymously. Want to search Bing? !b query. Google? !g query. Scratch this, I remembered wrong what those do.
I do believe there's a setting to aggregate the top results from several different engines as the default search algorithm.
Just put your bang in front of the rest of the search you want to do on that site:
!g why doesn't Google use bangs?
!ddg Why does Duck Duck Go use bangs?