Research the best parts for your specific purpose, order the parts, and build it yourself. For my use, which is predator hunting, I prefer a 16"-18", midlength gas, with a .223 Wylde chamber, flat top, with a 3-9x-40mm scope. I'd spend my money on a good barrel, good trigger, and decent glass. I think you could put together a pretty nice hunting AR for around $600 (not including optics)