I found its better to hire the people yourself and pay them more than they would get at some of these firms. the biggest problem with some of these support firms is turn over. So you have a dedicated decent staff helping your clients and then they are gone, so a new guys comes on board and starts over. if you can try to get a dedicated staff (even offshore or remote, etc) and pay them properly it works out better than going through all these support firms.
i should also state, not all are bad, there are some good ones, and they typically charge a bit more.
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