There seems to be a myth out there that you can improve the trigger by replacing the spring with a lighter one or even cutting it down as well as removing the pig-tail spring. All of these will in NO WAY improve the feel or weight of the trigger. This will only result in unreliable trigger reset. A simple way to prove this to be true is to remove the slide and pull the trigger.

The weight you feel is from the striker, as I mentioned before you could replace the striker spring but you may get light strikes. The only way to improve the feel would be to do a fluff n buff or what is also know as the famous .25 trigger job. Even this can prove very harmful if you are not very careful.

The Sigma trigger feels the way it does because it was designed as DAO no matter what you do this fact will remain. Honestly the trigger feels great breaks clean and constantly. The Sigma will make you a better shooter as it teaches you proper trigger control.