You would do to increase the SERP for this site http://www.604cleaner.com for it's keyword term. I'm telling ya it was on top 2 once.
You still are at number 6... In such a situation, I'll suggest you to keep a close eye on your competitors. Analyze what they are doing to come up on top. With some research on that, I think you should be able to retain the spot soon.
Content is very important, but without links it won't get you far.. you need to use quality content to obtain more links and only the combination of both will drive your serp better.
Do link building take pr4 or higher links .They push your site ranking a lot .You can do article posting & press release at good pr sites to get back links.
Try to analyze a backlink profile of your comeptitors, tool MajesticSEO.com could helps you (for low fee). You can see the competitors backlinks in the reports and try to get the same ones.
SEO Off page work is the key to get success in SERP. So make quality back links using your anchor text and improve your page rank.