I’d spend $600 and get a Kel Tec SU-16 rifle. Reliable, gas-piston based, light (5 pounds or less - half the weight of an AR), and made in the USA. Save the extra money for a dozen PMAGs and 500 rounds of ammunition!
OK, I don’t get it. I have never been remotely tempted to buy anything that says Kel Tec on it because I tend to buy quality and believe that with firearms, you get what you pay for. There is a reason that Kel Tec products are cheap and it is not the extra quality that goes into them. Personall, I would much rather pay $7-800 for a DPMS or Double Star AR-15 than save a few bucks buying a Kel Tec.