Hello, new to this forum and to ARs in general.  And I have a few questions.

I spent about a decade in the Marines, however, and competed in Division Matches a few times.  Enough to get a taste for competition.  After a few years without an M16, I'm looking at getting a black rifle of my very own.

My question to you is which rifle do I get?  I see that Bushmaster and Rock River Arms offer complete competition rifles, but could I build my own for a lot less money?  Would it be worth it to start off with a rifle that I know is going to be good and then modify it the way I want to achieve excellence?

I'm also very interested in the possibility of purchasing an M4 style upper that I can simply switch out with my competition upper for home defense purposes.  Somebody told me that you can't necessarily just switch uppers like that.  I was hoping to have one lower and two uppers that would basically make two different types of rifles available to me for a lot less money than buying two complete rifles.

My last question is whether or not the end of the ban will be affecting prices?  I don't particularly need or desire any of the "evil" features that were banned, so is it possible that I'll be able to get a rifle a bit cheaper because of this?