I would say it really depends on how well your agent can write your essay, which is the most important component of your application. I understand 90% of agents in the market suck. They don't speak English well, they don't have good writing skills and they don't even have overseas experience. I know several agents who have master degree in English from the Top3 universities in China and their writing skills are fu*king weak. So if you dont want to boost your gmat higher, I would suggest you pay a lot more effort on your essay and dont trust the fu***cking stupid agents (not all agents, but at least 90%+).