This sounds to me like a perfect AdWords Use Case, but only if you have a reasonable budget: few thousand dolars per month. If you want to know more about it, I suggest you read this book: "Advanced Google AdWords" by Brad Geddes. It really opened a lot of new perspective for me.
You can also try to do a lot of SEO and there is another book I can suggest to you: "The Art of SEO: Mastering Search Engine Optimization" by Eric Enge, Stephan Spencer, Rand Fishkin and Jessie Stricchiola.
Of course all the above suggestions from @Julianflynn, @CanarsieBK and @veikoh are great also. Hope this helps, would be glad to know how everything turns out.
Ciprian BORODESCU
CEO @ Webcrumbz.net
http://www.webcrumbz.net