Joe Kissell from Macworld USA has published an article about serious (re)search on the Internet. Besides meta search engines he also mentions DEVONagent as a power solution:

If you’re doing extensive research, consider a high-powered tool such as Devon Technologies’ $50 DevonAgent. In addition to being a stand-alone Web browser, it’s a full-featured research tool. DevonAgent lets you create complex searches that include Boolean operators, proximity terms, and filtering—spanning not just a few search engines but as many as you like.

Read the article yourself.