www.spikestactical.com Great company with GREAT affordable products.
Upper 16" DS-4 for sensibly priced uppers.
Do yourself a favor and don't spend too much on an AR as they are not ever going to be as accurate as your favorite bolt gun. Buy something you can afford that functions well. I like AR's but I have learned that a $500 quad-rail does absolutely nothing to improve my accuracy. Have fun!