I've got a lower on the way from Pete-in-NH, now I'm looking for a lower parts kit.  Are there big differences between them other than price?  What does a two stage trigger do differently?  Is it worth the money for just target shooting?  

I've heard some parts will hold up better than others.  I'm sure you'll get some recommendations with better deals, but if you stay with the big-name rifle manufacturers you'll be OK for quality.

As far as the trigger: a 2-stage trigger has, well, two stages--the first is most of the travel and weight, then the second is just a little bit more.  Once you get to the end of the first stage the second feels like a really light trigger.  It's popular with the Highpower and varmint shooters.  Not so good for IPSC-type shooting.  For just targets & plinking it's probably not worth it.