I recommend one of the PSA complete uppers with the 1:7 chrome-lined bore. It seems many of their uppers are out of stock right now, but they have a 20" PSA with BCG/CH for $449 as of the time of this posting
That is an excellent deal for a rifle gas system and CHF barrel, basically as close as you can get to a true M16 upper.
Then Add one of their lowers for less than $200, and you have a complete rifle for around $700 and money left over for your optic. Keep in mind you'd have to wait at least 14 business days for shipping, so if you don't mind the wait its a good deal.
If they have something you want in stock, be prepared to jump on it right away as their stock is limited.
But if you want a rifle now, then the M&P Sport is a great AR. It lacks a few conveniences; you will have to decide for yourself if that is important for your uses or not. I did own a Sport this year with the new 1:9 barrel and it was still a great rifle.