Good parts for building an AR-15?

I am going to build an AR-15, I don't want to go through the trouble of embling the kits so i'm planning on just buying the complete upper and lower haves. The lowest price ive seen on a complete lower is from stag arms ($290) are they any good? Are there any lower priced models and would the stag receivers accept any upper half say from model 1 sales or some other place?