But to answer the question: If you're going to get into a fight with an elephant, the trick is to avoid being directly in front of it when it charges. Yes, you can compete -- but compete by doing something different, not by duplicating what they're already doing.
I think maybe you could start jetting (it's an accelerated version of planing) to compete with big companies by leveraging open-source finance messaging products like RabbitMQ instead of starting from scratch. Then you can concentrate on new functionality with a solid foundation.
You might want to invest in a spel-chekker, as well.
I certainly don't expect all YC readers to be native English speakers. I did try to be helpful (AMQP/RabbitMQ suggestion), but without knowing more details about your idea it is difficult to help. My company does quite a bit of work in the financial messaging area (as a user, not as a SaaS provider), so I'd like to hear more about your ideas.
As a 'guy in a garage,' I'm not sure a financial messaging product would be my choice to focus on, open-source or not. It is a rather difficult market even for well-financed companies with teams of programmers and salespeople. Isn't there another market where your skills might be better leveraged?