Do you think it's better to go with a BIG SEO company or one person that really knows what they are doing?

[Rus]

First of all, good job on attracting spammers. Everybody is going to chime in to convince you that their service is the only one that works.

Second, remember the saying that if you want the things done right, you do them yourself. You could accomplish a lot by spending some time and very little money.
Several things for you to do:
Optimize your site according to Google guidelines below. Following those guidelines will make your site more search engine friendly.
Utilize social media. Have accounts on facebook, twitter and such, get fans and followers for those accounts and post frequent updates.
Blog about your site. Open free blogging acounts on blogger or livejournal and post news, product info, customer testimonials etc. Be sure to include links back to the pages of your site. You could also look into blogging service like v6transition which is not completely free but it has some advantages over free blogs.
Finally, you could write artciles and press releases. The former is free, the latter is not free but inexpensive.

Good luck.