It's quite a simple task to optermise the site yourself.
use www.ranks.nl to find how well your keywords are placed and improve the rating of them.
Have keys words in links, bold, italics, headings, title of the site is important for a good ranking. Also find as many sites as you can where you can place a link to your site.
I did this with my company website and went from 15th in Google to 1st on 3 different search terms.
I'm just about to rework my web design company site, which curretly dosn't rate anywhere, so It'll be interesting to see how it does.
checkout the sitepoint site for loads of good SEO tips.
you have to think about where they are generating the traffic from.
Its one thing to increase traffic to your site but you need to know where that traffic is coming from.
I don't know the company you linked to or anything about them but in general terms is the traffic 404, pop under, paid to surf or even automated bots? Is the traffic quality?
You may be better using the money to buy a few text links from sites that are in your niche. That way you'll get targeted traffic.