I've used many agents' service, but so far, Kevin from LEEO visa service did the best job. I am more than happy with his work and as a sign of gratitude i just wanted to mention him here. I submitted my passport to him a week ago, and it took only 5 work days to get a 1 year extension. The price was reasonable and no down payment was needed. I was very busy on the day I received the message that my visa was ready, so he even came to my office to give me my passport back. I really did not expect this level of service.
I don't want to discuss any details, but if you have questions, just PM me and you'll get your answers.