All depends on your style of shootin'. If you are one of those who is going to take time to set up for a shot, dial it all in on your optics, watch your breathing, and squeeze through the takeup and then the shot - for MOST of your shots, then you should consider a 2-stage.
If like most, you are out there popping clays, water bottles, the occasional prairie poodle or ground hogs, target shooting, or just have it ready for 2012 and the arrival of the zombies, then I'd say get a smooth single stage.
For my HD stick, it is a very reliable and smooth single stage by Bill Springfield. The stick next to it has a #3 Timney trigger in it, again very smooth and reliable. And the one that is next to my bed has a Geissele trigger in it, and is the best I have ever felt. I CAN
tell the difference between them, but would put my life or my family's lives on the line with any of them. I do have over 1000 rounds through them, with no issues, so I feel pretty secure that they will go bang when need be.
As for the kits, figure about $60-70 for a lower parts kit, and that will normally come with a mil-spec service trigger. Now, you could ditch that if you choose, and get a different trigger. OR...you could do like some have, send that trigger to Bill Springfield and have him tune it up the way you want it. Yes, it will cost you a little more $$, but you will have a very reliable and very smooth trigger. OR...you could buy a lower parts kit from Bill that will come with one of HIS triggers already in it. Bill Springfield Trigger and LPK
OR...you could order a lower parts kit from ADCO, the White Oak LPK, which does not come with a trigger, for $40, then buy whatever trigger you want. Adco WHITE OAK LPK
So there are a few options for you to consider. Rainier Tactical - AR Trigger Assemblies
I'm sure there are lots more out there.