Does anyone know of a reliable discount international airfare company?

I have been researching the cheapest way to book the flight I need to Chile in November. I found the exact outbound and inbound flights on different websites, as well as the airline's sight, but doing it from an outside company seems cheaper. I've found the best fare at cheapoair.com, but googled them and found the feedback on them to be about 90% complaints. I need good advice of REAL and RELIABLE companies to check out. Thanks!