As far as what rifle to buy you have to ask yourself one question first..... What is the purpose of the rifle?
If the rifle is just for target shooting than anything will probably work. If the rifle will be used for home defense then you should really look into a higher end model than builds them correctly. All of the cheaper brands cut corners to save cost when they make their rifles.
The rifles that I believe are good to trust your life with are:
To a slightly lesser degree:
Smith and Wesson
Spikes (Actually makes a really good rifle but has some shady business practices)
Any of the Tier 1 rifles are good enough to go into combat with. Actually several on that list due on a regular basis.
You can get a Colt 6920 (the civilian version of the M4, only difference is the barrel is 16 inches instead of 14.5 and not auto switch) at Walmart now for just over 1000 and you can find them online for cheaper sometimes.
If you buy the lower reciever seperately you can get a BCM for around 850 bucks.
If I was in your shoes I would buy the lower reciever locally and go online and buy a complete upper from BCM. Total with bolt carrier group should run you right around 850-900.
Looks like their Bolt Carrier Groups are out of stock right now but you can see the price.
Here is a BCM video featuring Travis Haley. Doesnt really add anything to the discussion but its cool
Im personally a huge fan of Colt. My personal Colt has a lot of useage, not as much as Id like lately but thats about to change. I clean mine every thousand rounds or so. ARs need to be lubed, not necessarily clean.