I use AstroGrep (http://astrogrep.sourceforge.net/features/) which is a great tool for searching for text inside files, but from the looks of it "add searching in archived files" is a possible upcoming feature so won't be much use to you for what you're trying to achieve. But worse case scenario you might have to extract your archive files first before searching, but I know that isn't always an option if you have concerns with the amount of files or file sizes are huge.