What are you going to use it for?
I just picked up a Bushmaster 16" M4 ORC from Cabela's for $879. It's a "base" model, shoots both .223 and 5.56, and can be easily modified. The model I picked doesn't have any iron sights, it's "optic ready", which means you would put on a scope right away. Most people I've heard from swear by their irons and say that you should always learn to shoot with them first.
Anyways - CMMG is running a "bargain bin" special. $570 for a complete rifle. That's using an unknown upper and a mix of lowers (CMMG, DPMS, or Doublestar) - I've heard nothing but good things about the CMMG or DPMS, unsure about Doublestar.
Anyways - from what I've read, everyone who has ordered one of these rifles has been really happy with them. Most people have reported getting a rifle with all new parts,etc.
Their site is at: http://cmmginc.secure-mall.com/shop/index.php?cat=33&shop=1&
I was debating between this deal at first too... I ended up getting my Bushy because Cabela's had them in stock and I could walk out of the store with it the same day. These deals need shipped to your FFL, etc.
Anyways - if you just want a black rifle to mess around with, you won't find a better deal than these bargain bin ones... Can you piece one together for that price? Maybe... But I wanted a complete one first, before I try my luck at building one.