Just stick to one site Berner.
The SEO company you employ "should" also be responsible for researching new key word opportunities within your industry (no just you helping them), and "should" assess the kind of traffic you "may" achieve as your project progresses. Assess competition is crucial, or you could be wasting your time.
Different pages on your site can be specifically targeted for certain industry "key words" and "geographical locations."; some competitive and some may not so.
All this depends on the strategy your guys employ..
For example, go create a page on your site specifically for individual case studies. What did you do? Where was it? What was the outcome? How does this benefit new customers? All these questions can help achieve great content for your customers, which is great for SEO.
