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You definitely seem to understand what you type of links you need. Also understand, link building is difficult and you get what you pay for. Choose a company that doesn't BS you. Don't look for guaranteed # of links or things like that. Ask them what techniques and ideas they have. Go from there. There are no result guarantees in this field, but you can guarantee honest hard work and the creation of a good plan. Sometimes, one good link can be better than a ton of low-quality ones. Not to mention bad links can actually get you in trouble.