Well, since you've got a landing page, PPC, hands down is going to be the fastest most cost effective solution. Yet given your niche, I can understand why you might find it tough to go PPC.
If you haven't already, I would still do a small targeted campaign to see which keywords convert. It will same you a lot of wasted time and effort when it comes to article marketing.
To go ahead with the article marketing:
1. I would come up with 10-20 solid articles and post those to ezine articles
2. Take each one of those original articles and mash them up to create another 5 derivative articles from each, those I would post to the other article directories.
3. Next, I'd make a wordpress blog in a folder/subdomain on the same location as your landing page i.e. "yoursite/blog" Using the Write Again plugin (available from one of the guys on this forum) you can pump those articles into the blog with some feeds related to your keyword. This will help boost the ranking of your landing page in the rankings.
4. Ping and promote the blog
5. Create an e-mail feed from the wordpress blog and post it to a blogger blog
6. Make a You Tube video or two showing the survey sites you are promoting and link those to the landing page
7. At this point, its probably been a while since you've looked at your articles, so grab them again, give them some edits and post the edited versions as a series of Squidoo lenses.
8. Finally, gather all this content you've generated, turn it into some sort of downloadable pdf and distribute on torrent sites and as an opt-in download from your wordpress blog (might as well start building a list at this point)
Remember, with article marketing 90% of it comes from how compelling you can make the headline. It's the great, shocking headlines that get the clicks and the downloads. In the body texts, give away your one best piece of information and people will find the landing page link irresistible.
Needless to say, it's a lot of effort to build bum campaigns. Outsource where you can, and remember it takes time to fully see the benefits of article marketing. You'll get results, but they will only be a good as your landing page converts so make sure you've got a winner before you invest the effort.