How much SEO do I need?

[Vanessa]

I have an online biz and it's been growing slowly and steadily but extra traffic would be great. I've done a lot with keywording, meta tags and descr., linking anchor text, keeping text relevant and fresh, social bookmarking and networking, using press releases, landing page and check out cart page optimization etc.

Now that I'm at the next stage of growth, I'm wondering if I need to engage the services of an SEO company. There are so many and for a small biz, they're quite costly. Are these services really going to help or should I just keep doing what I'm doing? I'm sure they're trained and know a ton of stuff I don't plus the one thing they say they'll do that is a bit beyond me is backlinking to my site from authority sites.

How much SEO do I need to grow my business? Is it worth the monthly expense of hundreds of dollars?