RRA Stage 2 match.
Have it in both of my ARs and... WOW
It is quick and smooth, pulls with about 3.5 lbs of force, but this is what I like the most: it is a highly recognizeable 2nd stage: you pull back and it stops (like on the M&P trigger if you hit the safety), and requires just a tad bit of force to fire.
It also has increased pins to keep it in there nice and firm.
ETA: when you come to Houston, if you don't feel comfortable putting it in by yourself, i'll do it with you at the range, so you can tell the difference between the triggers. Heck, we can even take out my ENidine ARrestor and put it in yours to see what you think