Upgrading your trigger all depends on what you like and are familiar with...single stage or 2 stage. It also depends on how much money you're willing to spend on a new trigger. Me, I like single stage triggers. I'm currently using a DPMS stock trigger in my AR, but like you I'm thinking of upgrading my trigger, but I'm not willing to part with 150 or more dollars for that trigger. The 2 options I've found, with great reviews from other shooters and forums, is either Bill Springfield or the Mega Tactical trigger. From what I understand you can't go wrong with either one. On top of asking other shooters, be sure to do your own research on what you want. Other shooters have their own preferences...just because they like something and haven't had any problems with it, doesn't mean it's the best option for you.
United States Marine Corps '94-'00
“No person was ever honored for what he received. Honor has been the reward for what he gave.” -Calvin Coolidge
"The deadliest weapon in the world is a Marine and his rifle." -Gen. John "Black Jack" Pershing, U.S. Army