Hello kinhon, Why don't you try Svitla? Well I know there are many more online providers now but you should know this that all software consulting farms are not good and you won't get the best services from the local provider. Svitla, Which is now one of the best software consulting firm in the online sector.
They are giving their best services to their customers. When you will need specialized expertize they are with you.If you need to manage an extension team for you they are also with you. They also giving creating software or developing services.Check Svitla Systems - software consuting service for know about their cost because i am not pretty sure about their costs but i heard some good reviews about them on internet.