Fairly new to the world of ARs. From reading posts here, it seems like most people spend $600 - $1,500 for an AR15, and seems like everyone customizes theirs. But I bought an S&W M&P15 22 for $330 online, brand new in box. I know "you get what you pay for", but does S&W really make a "cheap, get what you pay for AR15"? What can I expect in terms of lack of quality in a sub $500 M&P15?