In my opinion you should rethink your marketing strategy in terms of Inbound Marketing instead of SEO/SEM. Of course that SEO and SEM are key components of the strategy. However, I’ve seen that some businesses go to a cheaper service because someone else offers more visits or better ranking but sometimes without generating more sales at the end. What is required to generate more qualified leads that generate better ROI.
For more information about Inbound Marketing: http://www.hubspot.com/inbound-marketing
Our blog is this one: http://blog.gdlsystems.com It is also about Inbound Marketing however it is in Spanish so I recommend the HubSpot’s link.
We are an agency in Guadalajara, México. We get the best results working with customers in our city. So even when an oversees provider could work, my recommendation is that you look for one that is close to you even when it could cost more money at the beginning. Marketing is about generating more qualified leads that in turn generate more money. Cheap provider could at the end generate less money.