Dan,
For this letter, I might suggest testing an "If / Then" style of headline...
"Promote anything online" requires that you break down the "hype-o-meter" of your prospect...and the If / Then headline does a good job there.
You may also consider an advertorial style of approach with this.
Ben started a thread, I forgot which one unfortunately, that contained one of those ads as a download.
Ben just might...put that link here too.