As already mentioned above - a well tuned complete JP package (hammer, trigger, disconnector, springs, pins, etc.), I say this because you can also utilize a JP trigger, disconnector, and springs with your factory hammer & pins. However, the results will not be as good as, the JP hammer produces an incredibly fast lock time and glass rod break feel.
In terms of modular drop in triggers - I love Timney's and Wilson Combat TTU's (I have both). My 2 Timney's break @ 3.0 lbs and my WC TTU breaks @ 3.5 lbs. Both feel incredible and ironically, the break on the WC TTU is so good it actually feels lighter than 3.5 lbs. I can't comment on the Chip McCormick drop in unit.
Finally, I don't have any experience with JARD triggers. However, I know & have read that you can get those set-up in the 2.0 lb range.
Keep us posted
AvsFan