For SEO, instead of article marketing with article directories I suggest you to go with guest posting. It is a commonly known fact that, not the no. of links but the relevancy of the link is counted by SE. SEO is all about the popularity. I personally believe that for SEO, the link which people are more interested is highly effective rather than link which people are not interested to click.
For e.g. imagine that you've submitted an article on article directory like ezinearticles.com or other related directory of your niche. Normally, within 24 hours time span, the article will not be viewed even for 100 times. The no. of click received will also be very less whatever the CTR is. So instead of submitting the article on a directory I suggest you to submit to a high traffic blog related to your niche. Since it will be featured on the homepage or the recent posts for at least a day/week you will get more views for the article and thereby more clicks to your link and thereby more traffic.
If your lone purpose is to get #1 rank for a semi-popular keyword and if your only strategy is article marketing, then you might get tired by submitting thousands of article within months. Getting #1 is quite difficult these days (I am not saying impossible). You can also get targeted traffic by submitting guest posts on the blogs of your niche.
Let me know what you think..