Just like Stubbs ^^ I knew I wanted $1500 in parts, but did not want to pay a custom AR shop to build it for me, since a lot of 'custom' AR's start at $1500 and go up from here.
Take a loot at my build thread and you can see that I have the same lower as you, I chose a lower parts kit from Palmetto State Armory
without the fire control group. I did this because I knew I'd either want a Geiselle* trigger or something better than mil-spec. I ended up with Geiselle's sister companies trigger the ALG Combat trigger. This way my "LPK" was around $100 and got a better than stock trigger with a decent lpk. ALG also makes a $45 mil spec trigger that has been polished to save even more coin and be in the $80 range for a lpk with a polished trigger.
Also, check Ebay for parts, I bought %90 of my parts *NEW* from their either at a lower cost or with free shipping, which can add up if your buying 10-20 parts at $5-10 extra for s/h.