Be very careful about how you invest in SEO. It's what I do for a living. SEO agencies are notorious for selling customers temporary rankings. Meaning they manipulate google and you look good now, but in the long run google figures out what you're doing and you're ****ed.
I would be very wary of any SEO company that makes lofty promises, like "#1 spot on google, guaranteed". If you ever want me to review a company, or work they've done for you, I can do some quick auditing of your site.
Also, since it is tough to find a good SEO company, let me recommend
Web Marketing Services | Web Marketing Company | SiteLadder. I don't work for an agency anymore, but I used to work for the guy that owns siteladder, and I actually currently purchase services from them myself (I can't do everything for my sites, so I outsource). They do legitimate, white hat SEO. The owner has like 10 years of experience programming and in SEO. It's really hard to find that kind of experience. It's usually one or the other, and the 2 go great hand in hand.
Also, I recommend Wordpress, especially if you will be managing it.