depends on what you are shooting it for and how much you will be shooting it. My AR is a tool I need it to run in very bad conditions. I need mid-length gas system, mil-spec BCG, Cold Hammer Forged barrel 1:7twist. Not everybody is as hard as I am on a gun. Here are some good choices for around $1k (prices are from cheaperthandirt). I have my eye on a Sig Sauer M400 price from about $600-$800 it's your basic rifle with a lot of really tough parts in it. Bravo Company, CMMG, PSA, Spikes's tactical, Daniel Defense, Smith&Wesson, Bushmaster, Armalite all make great guns and you get what you pay for.
Rock River LAR-15 Mid-Length A4 Semi Auto
What it has going for it- Price, mid length gas system and two stage trigger
http://www.cheaperthandirt.com/product/82078
Bushmaster MOE M4
What it has going for it- price, Magpul MOE furniture set, weight, back up rear sight.
http://www.cheaperthandirt.com/product/63789
S&W M&P15 MOE Carbine
What it has going for it- Price, Magpul MOE furniture set, Weight 6.5lbs
http://www.cheaperthandirt.com/product/58561
S&W M&P15 MOE Mid Magpul Spec Series
What it has going for it- Price, Mid length gas system, 1:8 5R barrel, flared magwellMagpul MOE furniture set.
http://www.cheaperthandirt.com/product/80161
Bravo Company USA MID-16 Mod 0- Probably the best buy.
What it has going for it- Price, 1:7 Hammer forged barrel, mid length gas system, BravoCompany there's nothing they don’t touch on a rifle.
http://www.cheaperthandirt.com/product/2-BCM750-121
CMMG AR-15 MOE
What it has going for it- Price, mid length gas system, 1:7 barrel, Magpul MOE furniture set, Good family owned American Company
http://www.cheaperthandirt.com/product/7-G55A5244
Colt LE6920MPFDE M4
What it has going for it- Price, Mil Spec, 1:7, , Magpul MOE furniture set,
http://www.cheaperthandirt.com/product/82397