No one can promise you top ranking without knowing everything about your website, niche, keywords and competition. Anyone promising you without analyzing these are just taking you for a ride. $1000 is very little if you are looking for true SEO.
I would advise you to get some top article writers and get best in class articles for the site, and then do the SEO work yourself. It is relatively easy if you have great content. Catch me on skype and I can give you some more pointers